Date and time

Each programming language has an i18n (internationalization) library that automatically localizes time and date strings based on a user’s locale settings/preferences. Time and date strings should never be localized manually by a designer, engineer, or translator.

The Product Internationalization team is responsible for creating app UI content in non-English languages by localizing externalized code strings provided by our Product Engineers.

Engineers must:

Atlassian uses US date formatting (for example: January 12, 2028).

When you’re handing designs over to engineers, you need to specify which date format length is needed. The i18n library API will use this information to format the date accordingly. Date and time formats should not be hardcoded.

There are 4 date format lengths: full, long, medium, and short.

The full date format is weekday, month, day, year.

A long date format is month, day, year

The medium date format is abbreviated month, day, year. Only use this format when space is limited.

If you need to abbreviate months or days, use the first 3 letters of the month or day.

Short format dates are written in digits.

In most cases, avoid short format dates as different countries use the date in a different order, which can cause confusion and effect readability and usability. In the US, 10-8-2026 is October 8, 2026, but in Australia and the UK, it’s August 10, 2026.

However, short format dates might be suitable for situations like data storage, sorting or filtering, or data export/import. If using, use the ISO 8601 international standard for numerical date format, which is YYYY-MM-DD.

Don’t use ordinal numbers (1st, 2nd, 3rd, and so on) in dates.

If you have a date range, use ‘to’ and not hyphens. For example: ‘2020 to 2024’. Hyphens are read out by screen readers as ‘hyphen’, which can lead to confusion.

An exception is financial years, which use a hyphen without spaces on either side. For example: FY2008-09

Use ‘and’ if a range is preceded by ‘between’. For example: He was in Paris between 2025 and 2026.

Show time in digits for precision and to give a clearer expression of time.

Specify to engineers which time format length is needed. The i18n library API will then format the time according to a customer’s account settings. Make sure time is not hardcoded.

Use a colon (:) to separate the hours and minutes (though this might change depending on a user’s locale and account settings).

Like dates, there are 4 time format lengths: full, long, medium, and short.

The full time format is hour, minutes, seconds, and time zone spelt out.

The long time format is hour, minutes, seconds, and the time zone initials.

The medium time format is hour, minutes, and seconds.

The short time format is hour and minutes.

The 24-hour format is useful for more serious communications, for example in the case of outages and security comms. The use of the 24-hour format is mostly system-driven by the i18n library API.

This format numbers hours from 00:00 hours (midnight) to 23:59 and uses 4 digits: the first 2 digits are the hours and the next 2 digits are the minutes. Use a colon (:) to separate the hours and minutes, though this might change depending on someone's account settings.

When writing timestamps, labels on graphs, or durations, avoid using zeros before the hour. For example: 5:29. not 05:29. Use a colon between the hours and minutes with no spaces on either side.

Format time using ‘a.m.’ and ‘p.m.’ when creating content like blogs, manuals, and instructions.

Where suitable, use ‘noon’, ‘midday’ or ‘midnight’ instead of ‘12 am’ or ‘12 pm’ as it makes it easier for people to differentiate between these times.

Avoid using ‘fortnightly’ and the prefix ‘bi’ to mean either 2 or twice, as these terms can be confusing.

Instead of:

There are also full, long, medium, and short format lengths when combining date and time.

In some cases, like when the exact date is less important, the easiest way to describe something that happened very recently is using the ‘ago’ format.

For future and past events, use approximate time by rounding down to the largest or most recent date or time.

You should always provide a way for people to see the actual timestamp, usually via a tooltip.

Style and punctuation for dates and time can change depending on locale and is determined by the i18n library API.