Unambiguous date & time
If I gave you an assignment due on 3/4, would you complete it by March 4 or April 3? US Americans would assume March 4, but Europeans would assume April 3.
Communicating with a globally distributed team requires clarity. Fortunately, the International Organization for Standardization (ISO) provided a common date format to remove ambiguity in 1988.
The ISO date format is human readable and visually sortable with the components arranged largest to smallest.
Traditional US American
3/28/2023 14:56:30 PM
ISO 8601 standard
Week numbers: 2023-W13
Week number dates are used commonly in manufacturing and by Europeans. They are indicated after a year with a W and a 2 digit week number.
I appreciate them as a progress indicator through the 52 weeks in a year.
Calendar apps typically have a way to show week numbers. Look for it under settings.
Keep in mind that ISO weeks start on Monday and week 1 of the year is the first week with a Thursday in it. Some years have 53 ISO weeks because Gregorian calendars do not evenly divide by 7.
Quarter numbers: 2023-Q1
This is non-standard, but still useful. Similar to week numbers, yearly quarter numbers can be indicated after a year with a Q and the quarter number.
Further reading for software developers
Time can be appended to a date. The standard provides increasing levels of optional specificity in the pattern of YYYY-MM-DDTHH:MM:SS.000.
base time with hours and minutes
Time zones are location and season dependent. However, time offset from Coordinated Universal Time (UTC) can be specified.
Examples of the same moment in time:
Z = zero offset, a shortcut for UTC
Dublin standard time. 0 offset is always positive.
San Francisco standard time, negative 8 hours offset.
San Francisco daylight saving time, negative 7 hours offset.