Official Guidebolt General Design Standard
Date Example: 2020-12-31
Time Example: T21:30:11
Combined Example: 2020-12-31T21:30:11
Consistent communication of datetime can save lives. Example, expiry-labels for food that spoils easily and dangerously.
Logic: ISO-8601 is practical and intuitive. It starts with the most useful idea (YEAR) for most applications. It has linear progression of granularity (YEAR then MONTH then DAY then HOUR...). It uses the symbol T, shorthand for time, to clearly separate date from time.