Date and time notation in Australia most commonly records the date using the day-month-year format (25 April 2024) and with the 12-hour clock (9:34 am) most commonly used, although 24-hour time is used for some applications–e.g. some public transport operators such as V/Line^[1] and Transport NSW^[2] use 24-hour time, although others use 12-hour time instead.

Australians typically write the date with the day leading, as in the United Kingdom and New Zealand:

• 25 April 2024
• 25/04/2024

The month–day–year order (April 25, 2024) is sometimes used, often in the mastheads of magazines, schools, newspapers,^[3][4] advertisements, video games, news, and TV shows. MDY in numeric-only form (04/25/2024) is rarely used.

The ISO 8601 date format (2024-04-25) is recommended by the government to be used when communicating internationally.^[5] It is also commonly used in software.

Weeks are most identified by the last day of the week, either the Friday in business (e.g., "week ending 19/1") or the Sunday in other use (e.g., "week ending 21/1"). Week ending is often abbreviated to "W/E" or "W.E." The first day of the week or the day of an event are sometimes referred to (e.g., "week of 15/1"). Week numbers (as in "the third week of 2007") are not often used, but may appear in some business diaries in numeral-only form (e.g., "3" at the top or bottom of the page). ISO 8601 week notation (e.g. 2024-W17) is not widely understood.^{[citation needed]} Some more traditional calendars instead treat Sunday as the first day of the week.^{[citation needed]}

There is disagreement in Australia over whether Monday or Sunday is the first day of the week, but Monday is considered to be the most officially correct answer,^[6] and is the correct answer according to the Common Locale Data Repository (CLDR), since its October 2021 release.^[7]

The Australian government recommends using the 12-hour clock (9:34 am), except where the 24-hour clock is more helpful in the context, such as in travel, scientific fields and the military.^[5] The government also recommends a colon as the separator, however the single period is still used in some contexts.^[5] They also suggest writing the noon/after noon qualifier as "am" or "pm" in lower-case without periods.^[5]