Dates and time

Dates and expressions of time need to be readable and clear, particularly in content that contains detailed timelines. Write, abbreviate and punctuate dates and times consistently so people can understand your content. Follow international and Australian standards to write dates and times for data systems and international communication.

Follow Australian conventions for dates

There are Australian conventions for writing dates in words and numerals, and in numeric formats. These conventions include how to sequence elements of the date.

Use numerals and words for dates in most content. Use numeric dates when space is limited and in content types like tables.

Combine numerals and words for dates in body text

In Australia, the conventional sequence for dates is ‘day month year’. Use this sequence when expressing dates in numerals and words.

For dates in body text, use numerals for the day and year and spell out the name of the month. Don’t include a comma or any other punctuation.

Spell out the name of the day if it is being used, but don’t include a comma after the day.

The names of months and days start with an initial capital because they are proper nouns.

Write this

  • 31 December 2020
  • Thursday 31 December 2020

Not this

  • December 31, 2020
  • Thursday, 31 December 2020

Insert a non-breaking space between the day and the month so they stay together on one line. A non-breaking space means that a line break will split the date before the year.

Keeping the day and month together allows people to identify the information appearing before the line break as a date.

Write this

  • Please find attached the new agenda for the extraordinary general meeting, 2 pm 8 November 2022. [With a non-breaking space between ‘8’ and ‘November’]

Not this

  • Please find attached the draft minutes of the extraordinary general meeting held in Sydney, 8 November 2022. [With no non-breaking space between ‘8’ and ‘November’]

Don’t use an ordinal number (12th, 21st etc.) when writing dates in body text.

Write this

  • 1 May 1997
  • Schedule 3 commences on the first 1 July after the bill receives Royal Assent. [Extract from an explanatory memorandum]

Not this

  • 1st May 1997
  • Schedule 3 commences on the first 1st July after the bill receives Royal Assent.

Incomplete dates

Follow the general rules above when writing incomplete dates. Spell out the month in words if you need to leave out either the day or the year.

Example

  • The winning yacht usually reaches Hobart on 27 December.
  • More than 1,700 jobs have been created since January 2018.

There is an exception to the general rule for writing dates in body text. If you refer to the day but not the month, use an ordinal number.

Don’t put the ordinal suffix (‘st’, ‘nd’, ‘rd’ or ‘th’) in superscript. Superscript can cause problems for people who use screen readers.

Write this

  • She will leave by the 20th.

Not this

  • She will leave by the 20th.

If you refer to the year only, use the full numerical year. Don’t abbreviate it.

Write this

  • 1945

Not this

  • ‘45
  • 45

Use shortened forms for dates when space is limited

Only use abbreviations if space is limited – for example, in tables, illustrations, charts and notes. Ensure that it is obvious to users which days of the week or months you are referring to.

The standard abbreviations for the days of the week are:

  • Monday – ‘Mon’ or ‘M’
  • Tuesday – ‘Tues’ (‘Tue’) or ‘Tu’
  • Wednesday – ‘Wed’ or ‘W’
  • Thursday – 'Thurs’ (‘Thur’,‘Thu’) or ‘Th’
  • Friday – ‘Fri’ or ‘F’
  • Saturday – ‘Sat’ or ‘Sa’
  • Sunday – ‘Sun’ or ‘Su’.

The abbreviations in parentheses are alternatives for the standard abbreviation they follow. Only use the alternatives when the context ensures their meaning is clear.

Note: Style Manual lists Monday as the first day of the week. This is consistent with the order of calendar days in a calendar week as defined in the international standard adopted by Australia.

The standard abbreviations for the months are:

  • January – ‘Jan’
  • February – ‘Feb’
  • March – ‘Mar’
  • April – ‘Apr’
  • May – retain as ‘May’
  • June – retain as ‘June’ or shorten to ‘Jun’
  • July – retain as ‘July’ or shorten to ‘Jul’
  • August – ‘Aug’
  • September – ‘Sept’or shorten to ‘Sep’
  • October – ‘Oct’
  • November – ‘Nov’
  • December – ‘Dec’.

Only use the shortest form of days and months – ‘F’, ‘M’, ‘N’ and so on – in limited applications. An example is a time-series chart where the context and order allow users to understand the difference between each capital letter.

Don’t use a full stop after shortened days and months. No full stop is the correct Australian Government style for all abbreviations, acronyms and initialisms and contractions.

Don’t abbreviate dates in body text

Avoid abbreviated words when writing dates in body text. Words written in full are usually easier to read and understand.

Write this

The Labor Party called an urgent conference on Saturday 22 December.

Not this

The Labor Party called an urgent conference on Sat 22 Dec.

Don’t write dates as numerals unless space is limited

Avoid writing dates entirely in numerals for general content. Use numeric dates only when space is limited (such as in tables).

Numeric dates can be confusing because their order and format differs between countries.

Use Australia’s conventional order of ‘day month year’ unless you are writing for users in a country that uses a different style.

Use a forward slash in numeric dates

Separate the numbers in a numeric date with an unspaced forward slash, using the format ‘day/month/year’. This format uses single digits for single-digit days and months.

Write this

  • 4/6/2021 [Australia: d/m/yyyy]
  • 7/12/2020

Not this

  • 12/7/2020 [USA: m/d/yyyy]
  • 2021-06-04 [Sweden: yyyy-mm-dd]

Numeric dates can have 2-digit elements

You can also use 2 digits for each element.

Only use this style for the year:

  • in financial data
  • if it is clear which century you are referring to
  • if users understand the order of the elements (‘day month year’ for Australian users).

Example

  • 07/12/20
  • 30/06/22

Whichever style you use for date formats, use it consistently.

Full stops in computer applications

Many computer systems and applications use a full stop in numeric dates. Use 2 digits for the day and month and 4 digits for the year: dd.mm.yyyy.

Example

  • 07.12.2020
  • 10.09.2021

Don’t use an apostrophe for decades

Write decades with an ‘s’ on the end. Don’t use an apostrophe to show the plural.

Correct

  • 2010s
  • 1980s

Incorrect

  • 2010s
  • 1980s

In more casual writing, you can use expressions such as ‘the eighties’. You can also use an apostrophe to show the missing numerals in a decade – for example, ‘In the 80s, all my jackets had shoulder pads.’

Use words for spans of years in body text

As a general rule, write spans of years in words, using ‘to’, ‘from … to’ or ‘between … and’. Write the years out in full, not as abbreviations.

Don’t replace the word between the years with an en dash.

Write this

  • the years 2015 to 2019
  • from 2015 to 2019
  • between 2015 and 2019

Not this

  • the years 20152019
  • from 20152019
  • between 20152019

Use en dashes for particular types of year spans

Government content often includes spans of years. Some year spans are easier to read and understand if they contain an unspaced en dash rather than words.

This is particularly true in content that contains multiple spans of years. In this case, using en dashes makes the content easier to scan.

Use an unspaced en dash for a:

  • financial year
  • calendar year
  • span of years in the titles of publications and programs
  • span of years written in parentheses, such as for a term of office and the years of birth and death.

Always include the phrases ‘financial year’, ‘financial years’, ‘calendar year’ or ‘calendar years’ unless the context makes the meaning clear. You can also introduce the relevant phrase at first mention and just write the year span, without the phrase, in later mentions.

Finally, exercise your judgement. Consider using en dashes for year spans when using words makes the content harder to read.

Example

  • This document includes expenditure and revenue estimates for the 2021–22 financial year. For comparison, the attachment contains estimates for 2020–21 and 2019–20.
  • The agency measures injury hospitalisations and deaths over 2 calendar years. Data showed a small increase in injury hospitalisations for 2017–2018 and 2019–2020. Injury deaths declined over the earlier period, but showed a marked increase for 2019–2020.
  • The library holds a reference copy of the Inclusion and diversity strategy 2022–24.
  • Alfred Deakin was Prime Minister for much of Australia’s 2nd Parliament (1903–1906).
  • Sidney Nolan (1917–1992) had 3 younger siblings.

Always use unspaced en dashes in spans of years. Don’t use forward slashes.

Write this

  • National Road Safety Action Plan 201820
  • Australia’s energy consumption rose by 0.6% in 201819 and fell by 2.9% in 201920.

Not this

  • National Road Safety Action Plan 2018/20
  • Australia’s energy consumption rose by 0.6% in 2018/19 and fell by 2.9% in 2019/20.

Use words for spans of days and months in body text

As a general rule, use ‘from … to’ and ‘between … and’ in spans of days and months.

If it’s appropriate for your content, keep elements of the span together by inserting non-breaking spaces between them.

When you include a year, insert a non-breaking space between the day and month. A non-breaking space keeps the day and month together while the line break splits the date before the year.

Example

  • Parliament is scheduled to sit fromto 21 December. [Non-breaking spaces between ‘3’, ‘to’, ‘21’ and ‘December’]
  • We will do snap inspections betweenand 8 September. [Non-breaking spaces between ‘6’, ‘and’, ‘8’ and ‘September’]
  • The exhibition will run from 30 November to 23 February 2022. [Non-breaking space between ‘30’ and ‘November’ and between ‘23’ and ‘February’]

Use en dashes for spans of days and months when space is limited

Only use en dashes for spans of days and months if you have limited space. This could be in display text, tables, lists or in social media posts.

But also exercise your judgement – consider using en dashes if using words makes the content harder to read.

The en dash is spaced when the day and month appear on both sides of the span.

Example

Exhibitions in 2024 The power of the comma 6 Feb – 30 Jun; 9 am – 4 pm daily

The en dash is unspaced when the month only appears at the end of the span.

Example

  • Symposium Series 2025

    Plain language: 3–5 March
    Accessible tables: 9–11 June
    Content design: 8–10 September

Refer to specific days, events and periods with capitals

Treat specific days, public events and periods in history as proper nouns and use initial capitals. Use lower case for ‘the’ and any prepositions, unless they are capitalised as part of a proprietary name.

In body text, use lower case for generic terms like the names of seasons –‘autumn’ – and astronomical events such as ‘equinox’ and ‘solstice’. Write ‘century’ and ‘centuries’ in lower case.

Holidays and events

Use initial capitals for all institutional holidays, religious days and public events. Follow the capitalisation of proprietary names.

Example

  • New Year’s Day
  • Good Friday
  • Ramadan
  • Yom Kippur
  • the City2Surf
  • the AFL Grand Final
  • Labour Day
  • the Adelaide Festival
  • Party In The Paddock 2024
  • Anzac Day [‘Anzac’ stands for Australian and New Zealand Army Corps, but only takes an initial capital. The acronym appears in legislation with an initial capital and this has become the commonly-used form.]

Periods and events of historical importance

Use initial capitals for specific periods and events of historical importance, but not when you abbreviate them to a generic term.

Example

  • the Renaissance
  • the Bronze Age
  • the French Revolution, the revolution
  • the Battle of Long Tan, the battle

World wars

There are 2 acceptable styles for referring to the world wars.

Use either style, but be consistent in your content.

Example

  • First World War, Second World War
  • World War I, World War II [With roman numerals]

Use 2 non-breaking spaces to keep each name together on one line of text.

Write ‘World War I’ and ‘World War II’ with roman numerals.

The accepted way to write most roman numerals is by typing letters of the alphabet. Use a capital ‘i’ – I – for the world wars.

The Style Manual acknowledges that the house styles of some government agencies require the use of the arabic numerals ‘1’ and ‘2’. User research will always guide an agency’s style choices. Our recommendation to use roman numerals comes from corpus evidence.

Shortened forms for world wars

In content with many mentions of the world wars, you might decide to use a shortened form. Write the name of the war out in full the first time you use it. Include the shortened form in parentheses immediately afterwards and use the shortened form from then on.

Use roman numerals in the shortened form.

Example
  • The Second World War (WWII) started in 1939. Many Australians died in WWII.
  • World War I (WWI) started in 1914. Many Australians enlisted for service in WWI.

Eras and periods

Use initial capitals for the actual name of a geological era or period but not for broad historical and cultural times.

Example

  • the Lower Jurassic period
  • the Mesozoic era
  • the colonial era
  • baroque ornamentation

Centuries

Use numerals, not words, for centuries. This is an exception to the rule for ordinal numbers.

Write ‘century’ and ‘centuries’ in lower case.

Don’t use shortened forms, such as 18C or C18, unless you have limited space.

Don’t use superscript for the ordinal suffix.

Write this

  • the 18th century
  • in the 2nd and 3rd centuries
  • a 19th-century writer
  • an 8th-century monastery

Not this

  • the eighteenth century
  • in 2C and 3C
  • a nineteenth-century writer
  • an eighth-century monastery
  • an 8th-century monastery

Use CE and BCE to represent the common era (CE) and the time before the common era (BCE). There is no ‘year 0’ in this system. The years progress from 1 BCE to 1 CE.

Write ‘CE’ and ‘BCE’ without full stops and with a non-breaking space separating them from the year or century.

Example

  • 44 BCE
  • 1452 CE
  • the 3rd century BCE
  • the 3rd century CE

Seasons and seasonal events

Use lower case for the seasons and recurrent seasonal events.

Example

  • winter
  • summer solstice

Use numerals for times of day

In most documents, numerals give a clearer expression of time. Write times of day using numerals, especially when you need to convey precise times.

Use a colon between the hours and minutes. The use of a colon as the separator, rather than a full stop, reflects a shift in contemporary Australian usage.

A colon ensures that the time isn’t confused with a decimal number.

For example, ‘10.50’ can be read as ‘10 and a half’ as well as ‘50 minutes past 10’. Screen reader users will probably hear ‘10.50’ as ‘10 point 5’.

Example

  • The bus leaves at 8:22 am.
  • The broadcast will run from 9:45 am to 11:45 am.

Times using ‘am’ and ‘pm’

The initialisms ‘am’ and ‘pm’ come from the Latin phrases ante meridiem (before noon) and post meridiem (after noon).

Write ‘am’ and ‘pm’ in lower case. Separate the numbers and the initialism with a non-breaking space.

Don’t use ‘am’ and ‘pm’ with words that duplicate their meaning, for example ‘morning’ and ‘afternoon’.

Correct

  • Please respond by 10 am tomorrow.
  • Let’s meet at 6:30 pm.

Incorrect

  • Please respond by 10 am tomorrow morning.
  • Let’s meet at 6:30 pm in the evening.

You can use 2 zeros to show the full hour, but they aren’t essential. Use 2 zeros if that is consistent with other expressions of time in your content, such as in running sheets.

Example

  • 9 pm
  • 9:00 pm

Noon, midday and midnight

Use ‘noon’, ‘midday’ or ‘midnight’ instead of ‘12 am’ or ‘12 pm’. This makes it easier for people to understand the time.

Write this

  • We have extended the closing date to midnight Friday 7 October 2022.

Not this

  • We have extended the closing date to 12 am Friday 7 October 2022.

Write ‘o’clock’ only when you quote someone directly or transcribe a recording. In these situations, use numerals and the word ‘o’clock’.

Example

  • ‘The minister is speaking at about 10 o’clock,’ they said.

The 24-hour clock

Use the 24-hour clock if it helps people understand your content. This is important when referring to times in these contexts:

  • travel
  • certain scientific fields
  • the armed services
  • content written for countries using the 24-hour clock.

The 24-hour clock is also useful in content where space is limited. This is because it uses fewer characters than times with ‘am’ and ‘pm’. For this reason, it is often used in timetables and schedules.

This system numbers the hours from 00:00 hours (midnight) to 23:59. It always uses at least 4 digits. It can have 6 digits if seconds are included:

  • The first 2 digits are the hours.
  • The next 2 digits are the minutes.
  • The last 2 digits are the seconds, if you include them.

Always use a ‘leading zero’ for hours under 10 – for example, write ‘05:30’ not ‘5:30’.

Use a colon to separate the hours, minutes and seconds in the 24-hour clock.

Example

  • 00:45 [12:45 am]
  • 07:38 [7:38 am]
  • 23:18 [11:18 pm]
  • 23:59:17 [11:59:17 pm – includes hours, minutes and seconds]

Don’t add ‘am’ or ‘pm’ to times written in 24-hour clock format.

Write this

  • 06:45
  • 23:18

Not this

  • 06:45 am
  • 23:18 pm

Some government agencies that produce technical and scientific content don’t use a colon for the 24-hour clock – for example, 2300 and 0430. This is the ‘basic format’ used for international communication.

If space is limited and you use the 24-hour clock in general content, we recommend inserting a colon for clarity. This is the ‘extended format’ used for international communication.

Time zones

You might need to define which time zone you are referring to.

Time zones are usually written with the 24-hour clock.

The main Australian zones are:

  • ACST (Australian Central Standard Time)
  • ACDT (Australian Central Daylight saving Time)
  • AEST (Australian Eastern Standard Time)
  • AEDT (Australian Eastern Daylight saving Time)
  • AWST (Australian Western Standard Time)
  • LHST (Lord Howe Standard Time)
  • LHDT (Lord Howe Daylight Time).

Daylight saving time is not observed in the Northern Territory, Queensland and Western Australia.

There are also time zones for some Australian external territories.

Example

The meeting will commence at 15:30 AEDT on 17 November 2022.

Coordinated Universal Time

Coordinated Universal Time (UTC) is a time standard used as the basis for regulating world timekeeping.

UTC expresses the unadjusted local time at 0° longitude. It is not adjusted for daylight saving. Local standard time at longitudes around the world is represented by an offset to UTC.

UTC is based on International Atomic Time (TAI), which is a weighted average of atomic clocks located around the world, including in Australia. TAI does not take into account changes in the earth’s rotation, so leap seconds are occasionally added to UTC.

UTC is the standard and legal reference for times of day in Australia. The UTC(AUS) standard is maintained by the Australian Government’s National Measurement Institute.

Time zones are written as positive or negative offsets to UTC.

Write the initialism ‘UTC’, followed by ‘+’ or ‘−’, followed by the time offset to UTC in 24-hour system format.

Example

  • During winter, the time in Sydney is UTC+10:00.
  • São Paulo is in the Brasília Time Zone which is UTC−03:00.

Use en dashes for spans of time when space is limited

Only use en dashes for time spans if you have limited space. This could be in display text, tables, lists or in social media posts.

But also exercise your judgement – consider using en dashes if using words makes the content harder to read.

The spacing of the en dash depends on the elements of the span.

Use an unspaced en dash:

  • if the ‘am’ or ‘pm’ appears only at the end of the span
  • for spans of time in the 24-hour clock format.

Use a spaced en dash:

  • when ‘am’ or ‘pm’ appears on both sides of the span
  • if ‘noon’, ‘midday’ or ‘midnight’ appears in the span.

Example

  • Soccer training this Sat: 89 am
  • Available appointment times are:
    08:0008:15
    13:3013:45
    16:4517:00
  • Help desk opening hours:
    Monday to Thursday: 7 am – 4 pm
    Friday: 9 am – midday

Don’t combine words and the en dash.

Write this

  • Closed 11 am – 2 pm.

Not this

  • Closed between 11 am  2 pm.

Follow the manual’s number rules for duration

When expressing duration (lengths of time) in body text, follow Style Manual rules about choosing words or numerals.

This means writing the words ‘zero’ and ‘one’ and using numerals for ‘2’ and above. The rules also say to use the numerals ‘0’ and ‘1’ in specific situations.

For duration, the specific situations are likely to be when:

  • you compare numbers in a sentence
  • a sentence contains a series of numbers.

Write the words ‘zero’ and ‘one’ in sentences that don’t contain other numerals. Write the numerals ‘0’ and ‘1’ in sentences that contain numerals from 2 and above, or where all numbers show duration.

Spell out the units of time: ‘hours’, ‘minutes’ and ‘seconds’.

Example

  • There are 7 minutes and 30 seconds remaining. [Numerals for 2 and above]
  • The hearing adjourned for 2 hours. [Numerals for 2 and above]
  • The committee will break for lunch for one hour. [Words for zero and one]
  • Although we allowed candidates 1 minute to answer each question, most took over 2 minutes. [Numerals when comparing duration]
  • I noted faults at these time stamps: 0 minutes 45 seconds, 1 minute 4 seconds and 3 minutes 8 seconds. [Numerals for a series of numbers showing duration]

Use fractions written in words if users only need a general idea of values.

Only use decimal numbers if they are the best way to explain what people need to know. But be aware that some people might not understand the decimal’s time value. For example, 1.25 hours is 1 hour 15 minutes, not 1 hour 25 minutes.

It is usually better to avoid decimals and include the number and unit of time.

Example

  • The session finished about a quarter of an hour early. [Words for a fraction – gives a general idea of the duration]
  • I clocked her at 15 minutes and 12 seconds. [Easier to understand than 15.2 minutes]

    They broke the record by 0.04 seconds. [Numeral – a decimal gives people the information that is appropriate in this context. But the words by 4 hundredths of a second’ might be clearer to some users.]

Use shortened forms for units of time when space is limited

It is usually better to spell out the units that measure time. This is particularly so in general content. Only use short forms if space is limited and the short forms are easy to identify correctly.

If you need to abbreviate time, use the following units as shortened forms:

  • second – s
  • minute – min
  • hour – h
  • day – d
  • week – wk
  • month – mo
  • year – y or yr (Choose one and use it consistently in your document.)

The International System of Units – SI – is the international standard for measurement. The unit for second – symbol ‘s’ – is the SI base unit for time.

Other time measures are not SI units – but ‘min’, ‘h’ and ‘d’ are used with ‘s’ and recognised as legal units of measurement in Australia. They are listed in Schedules 1 and 2 of the National Measurement Regulations.

There are also commonly-used shortened forms for time measures – for example, ‘wk’ (week), ‘mo’ (month) and ‘yr’ or ‘y’ (year). These are not legal units of time, but are likely to be understood when used alongside other time units.

If your expression contains one time measure only, insert a non-breaking space between the number and unit.

Never add an ‘s’ to show a plural.

Write this

  • 35 s
  • 15 min
  • 6 h
  • 5 d
  • 3 wk
  • 8 mo
  • 2 y or 2 yr
  • [There are non-breaking spaces between numbers and units. There is no ‘s’ to show plurals.]

Not this

  • 35s
  • 6hs
  • 15mins
  • 5d
  • 3wks
  • 8mo
  • 2y or 2yr
  • [There are no non-breaking spaces between numbers and units. There is an ‘s’ after ‘min’, ‘hr’ and ‘wk’.]

But don’t space a number and its unit when your expression contains more than one time measure. Use a non-breaking space between each time value instead.

Never add an ‘s’ to show a plural.

Write this

  • 11min 12s
  • 7h 8min 30s
  • [There is no space between a number and its unit. There is a non-breaking space between each time measure in the expression.]

Not this

  • 11min12s [There is no (non-breaking) space between ‘11min’ and ‘12s’.]
  • 11 min 12 s [There is a non-breaking space between ‘11’ and ‘min’ and between ‘12’ and ‘s’.]
  • 7hs 8mins 30s [There is an ‘s’ after ‘7h’ and ‘8min’.]

Data systems support specific (and usually several) shortened forms for units of time. For example, hours might be: h, hh, hr, hours, hrs. They might also be case-sensitive or case-insensitive. You will need to check system specifications.

Avoid using ‘bi’ to mean either 2 or twice

The prefix ‘bi’ can be confusing when used with expressions of time:

  • ‘Bimonthly’ can mean either every 2 months or twice a month.
  • ‘Biannual’ means twice a year.
  • ‘Biennial’ means every 2 years.

Instead of using these words, be clear about the frequency and period of time you mean.

Write this

We meet once every 2 years.

Not this

We meet biennially.

How to combine dates and times

There is no fixed rule about the order of dates and times when combining them in body text. You can choose whether the date or the time should come first. The order doesn’t matter as long as the information is clear and the sentence flows logically.

But make sure that:

  • you follow the style rules for each element
  • the time doesn’t come between the day and the date
  • you use the same style throughout your document consistently.

Write this

  • They will appear before the committee at 3 pm on Wednesday 7 August 2024.
  • They will appear before the committee on Wednesday 7 August 2024 at 3 pm.
  • [There is a non-breaking space between ‘3’ and ‘pm’, no comma after ‘Wednesday’, and a non-breaking space between ‘7’ and ‘August’.]

Not this

  • They will appear before the committee at Wednesday 3 pm on 7 August. [The time appears between day and date.]
  • They will appear before the committee on Wednesday, 7 August at 3 pm. [There is a comma between day and date.]

Combining dates and times when space is limited

Use the same approach to combine the date and time when you have limited space. This might be in a table, social media post, or in a display or presentation context (display text).

We always recommend using minimal punctuation, but exercise your judgement. A comma between the date and time can make information easier to scan if you haven't used a preposition like ‘at’ or ‘on’.

You can also use shortened forms for the date. Only do this if you are sure users will understand what you mean.

Example

  • Lunch and Learn: Financial security in the 1980s
    Friday 1 March at 12 midday
    3rd floor seminar room
  • Lunch and Learn: Financial security in the 1980s
    12 midday, Friday 1 March
    3rd floor seminar room
  • Content Meetup
    Tue 23 Apr at 4 pm
    All welcome!

Meet standards for data systems and information interchange

Follow international standards when writing dates and time:

  • for international communication
  • to transfer data between systems.

The International Organization for Standardization (ISO) develops and publishes the international standard for dates and time format – the ISO 8601 series.

Australia and New Zealand have adopted the international standard. The Australia – New Zealand standard is Date and time: representations for information interchange. It is published as the AS/NZS ISO 8601 series in 2 parts:

  • Part 1: basic rules
  • Part 2: extensions

You can purchase copies of ISO 8601 and AS/NZS ISO 8601 from Standards Australia.

Standards are voluntary

International and Australian – New Zealand standards on dates and time are voluntary.

The standards ensure that data systems and humans can exchange date and time information internationally and across time zones in a recognised format.

A description of all the dates and times standards is beyond the scope of the Style Manual.

We cover these standards from Part 1: basic rules:

  • calendar date
  • ordinal date
  • local time of day
  • combined calendar date and local time of day.

We don’t cover Part 2: extensions.

Basic and extended formats

There are 2 format options for each standard: ‘basic format’ and ‘extended format’.

Basic format does not have separators between units of dates and time. Avoid using basic format in body text. It is easy for computers to read but harder for humans.

Extended format is also for computers, but it includes separators between units to make it easier for humans to read.

We show both formats in our examples.

Calendar date

The standard sets out a descending order of year (4 digits), month (2 digits) and day (2 digits) for a complete representation of calendar date.

The numbers can be unspaced (basic format) or separated by a hyphen (extended format).

Example

20201207 [Calendar date, basic format]

2020-12-07 [Calendar date, extended format]

ISO format is becoming more common, especially in software.

Ordinal date

Ordinal dates are often used when transferring data between data systems. This is because they are easy for simple systems to read.

Ordinal dates are not the same as ordinal numbers.

Ordinal dates have 7 digits:

  • The first 4 digits represent the year.
  • The next 3 digits represent the day.

This is the ISO standard. Some older systems might use 2 digits for the year, not 4.

Days are numbered from 1 to 365 (366 for a leap year). For example, 20 September is the 263rd day of the year (264th in a leap year) and its 3 digits are 263.

The ordinal date can be unspaced (basic format) or separated by a hyphen (extended format).

If you use dates in electronic data transfer, use basic format and don’t separate the numbers.

If people, rather than a computer, will read the information, use extended format and insert a hyphen between the year and day.

Example

Write 7 January 2023 as:

  • 2023007 [The 4-digit form for the year, basic format]
  • 23007 [The 2-digit form for the year, basic format].

Write 31 July 2020 as:

  • 2020-213 [The 4-digit form for the (leap) year, extended format]
  • 20-213 [The 2-digit form for the (leap) year, extended format].

Local time of day

The standard for a complete representation of local time of day starts with the letter ‘T’ followed by 2-digit numbers for the hour, minute and second.

The numbers can be unspaced (basic format) or separated by a colon (extended format).

You can omit the ‘T’ if there’s no possibility of confusion.

A ‘reduced precision’ time of 15 minutes after 7 pm in basic format – ‘1915’ – can easily be confused with the calendar year 1915. In these cases, it is better to write time of day as T1915 (basic format) or 19:15 (extended format).

Note: The format for local time of day doesn’t allow for daylight saving. The format showing daylight saving includes the time shift between local time and Coordinated Universal Time. This is beyond the scope of the Style Manual.

Example

  • 153020 [Local time of day, basic format – 15h 30m 20s, that is 20 seconds after 3:30 pm]
  • 15:30:20 [Local time of day, extended format]

Combined date and local time of day

Combine date and local time of day using the style standards set out above.

Always use the letter ‘T’ between the date and time.

The basic format for international communication is unspaced. The extended format uses hyphens for the date and colons for the time of day.

Example

  • 20230811T121505 [Basic format – 11 August 2023 at 15 minutes and 5 seconds after midday.]
  • 2023-08-11T12:15:05 [Extended format]
  • 2023223T121505 [Ordinal date, basic format – same date and time as above]
  • 2023-223T12:15:05 [Ordinal date, extended format]

Insert a non-breaking space correctly

You can insert a non-breaking space using the Unicode character U+00A0.

keyboard shortcut Ctrl+Shift+Spacebar in Word.

Release notes

The digital edition adds new content including rules and examples for:

  • date spans
  • time spans and lengths
  • shortened forms
  • Coordinated Universal Time
  • combined dates and times.

There is expanded guidance on standards for data systems and information interchange.

The digital edition changes the punctuation used with expressions of dates and time. There are no full stops for shortened forms of months and days of the week. This is consistent with the new general rule for abbreviations.

Unlike the sixth edition, but consistent with the Content Guide, the digital edition recommends using a colon rather than a full stop when expressing times.

The Latin shortened forms, ‘am’ and ‘pm’ do not have punctuation. This is consistent with the sixth edition and the Content Guide.

Consistent with the Content Guide, the digital edition recommends specifying noon or midnight for 12 o’clock (instead of using ‘am’ or ‘pm’).

The recommendation to express a date span using a phrase, rather than an en dash, aligns with the Content Guide.

Like the sixth edition, the digital edition recommends the use of non-breaking spaces between the day and month in dates. It differs from the sixth edition by recommending the use of a numeral with centuries. The digital edition recommends 2 acceptable styles for references to the world wars, while the sixth edition does not have an explicit rule.

The Content Guide illustrated guidance, but did not have explicit advice, on the use of spacing for dates and time. The use of a space between time and ‘am’ or ‘pm’ is consistent with the sixth edition, but a departure from examples given in the Content Guide.

About this page

Evidence

Australian Broadcasting Corporation (2024) ‘Wars’, The ABC style guide, ABC website, accessed 14 March 2024.

Biotext Pty Ltd (2024) ‘Date and time systems’, Australian manual of style, AMOS website, accessed 4 January 2024.

Bureau International des Poids et Mesures (BIPM) (n.d.) SI base unit: second (s), BIPM website, accessed 4 October 2023.

Butterfield J (ed) (2015) Fowler’s dictionary of modern English usage, 4th edn, Oxford University Press, Oxford.

Joint Standards Australia/Standards New Zealand Committee IT-019 (2023) Date and time: representations for information exchange. Part 1: Basic rules, AS/NZS ISO 8601.1:2021 (at February 2023), Standards Australia Limited/Standards New Zealand.

National Measurement Regulations 1999 (Cth), Schedule 1.

Oxford University Press (2016) ‘5.7: Events’, New Oxford style manual, Oxford.

Oxford University Press (2016) ‘11.3: Times of day’, New Oxford style manual, Oxford

Peters P (2007) ‘World war’, The Cambridge Australian English style guide, Cambridge University Press, Cambridge.

Treasury Board of Canada Secretariat (2024) ‘Times’, Canada.ca content style guide, Canada.ca, accessed 14 March 2024.

University of Chicago (2017) ‘8.113: Wars and revolutions’, Chicago manual of style, 17th edn, University of Chicago Press, Chicago.

University of Chicago (2017) ‘9.37: Numerals versus words for time of day’, Chicago manual of style, 17th edn, University of Chicago Press, Chicago.

University of Chicago (2017) ’10.39: Abbreviations for months’, Chicago manual of style, 17th edn, University of Chicago Press, Chicago.

University of Chicago (2017) ’10.40: Abbreviations for days of the week’, Chicago manual of style, 17th edn, University of Chicago Press, Chicago.

US Government Publishing Office (2017) ‘12.9.b. Clock time’, Government Publishing Office style manual, US Government Publishing Office website, accessed 30 March 2022.

References

Australian Broadcasting Corporation (2024) ‘Dates and times’, The ABC style guide, ABC website, accessed 7 March 2024.

Australian Institute of Health and Welfare (2023) Injury in Australia, AIHW website, accessed 15 August 2023.

Beard R (2013) ‘The past and future of Coordinated Universal Time [PDF 3.38MB]’, ITU News, 7:9–12, accessed 10 October 2023.

Bikos K and Buckle A (2024) What Is International Atomic Time (TAI)?, Time and Date AS website, accessed 14 March 2024.

British Broadcasting Corporation (2024) ‘World war’, News style guide, BBC website, accessed 14 March 2024.

Btb Translation Bureau (2022) ‘Numerical expressions’, The Canadian style, Btb Translation Bureau website, accessed 24 February 2023.

Bureau International des Poids et Mesures (BIPM) (n.d.) Annual reports, BIPM website, accessed 13 September 2023.

Bureau of Meteorology (2021) Daylight Saving Time and weather observations, Bureau of Meteorology website, accessed 13 September 2023.

Bureau of Meteorology (2014) Time conventions, Bureau of Meteorology website, accessed 7 April 2022.

Content Design London (2020) ‘Grammar points: numbers’, Content Design London readability guidelines, Content Design London website, accessed 24 February 2022.

Department of Climate Change, Energy, the Environment and Water (DCCEEW) (2022) ‘Australian energy update 2022’, Australian Energy Statistics, DCCEEW, Australian Government, accessed 2 August 2023.

GOV.UK (2024) ‘A to Z: dates’, Style guide, GOV.UK, accessed 14 March 2024.

GOV.UK (2024) ‘A to Z: times’, Style guide, GOV.UK, accessed 14 March 2024.

GOV.UK (2024) ‘A to Z: World War 1, World War 2’, Style guide, GOV.UK, accessed 14 March 2024.

International Organization for Standardization (ISO) (n.d.) ISO 8601: date and time format, ISO website, accessed 9 August 2023.

International Telecommunication Union (2024) ITU radiocommunication sector, ITU website, accessed 14 March 2024.

Lyons G (2019) Which day do you consider the start of the week?, ABC News website, accessed 3 January 2024.

National Institute of Standards and Technology (2023) NIST time frequently asked questions (FAQ), NIST website, accessed 14 September 2023.

National Measurement Institute (n.d.) Time and frequency services, Department of Industry, Science, Energy and Resources website, accessed 30 March 2022.

New Zealand Government (2020) ‘Numbers’, Content design guidance, Digital.govt.nz, accessed 30 March 2022.

Oxford University Press (2016) ‘10.2.6: Upper- and lower-case abbreviations’, New Oxford style manual, Oxford University Press, Oxford.

Oxford University Press (2016) ‘11.5: Date forms’, New Oxford style manual, Oxford University Press, Oxford.

Parliamentary Library (2017) ‘Anzac Day traditions and rituals: a quick guide’, Research Papers 2016–2017, Parliament of Australia website, accessed 20 July 2022.

Tavella P (31 July 2023) ‘Coordinated Universal Time: an overview’, ITU News Magazine, ITU website, accessed 10 October 2023.

University of Chicago (2017) ‘Dates’, Chicago manual of style, 17th edn, University of Chicago Press, Chicago.

University of Chicago (2017) ‘Time of day’, Chicago manual of style, 17th edn, University of Chicago Press, Chicago.

This page was updated Friday 21 June 2024.

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