Funny thing, in ISO 8601 date isn't separated by colon. The format is "YYYY-MM-DDTHH:MM:SS+hh:mm". Date is separated by "-", time is separated by ":", date and time are separated by "T" (which is the bit that a lot of people miss). Time zone indicator can also be just "Z" for UTC. Many of these can be omitted if dealing with lesser precision (e.g. HH:MM is a valid timestamp, YYYY-MM is a valid datestamp if referring to just a month). (OK so apparently if you really want to split hairs, timestamps are supposed to be THH:MM etc. Now that's a thing I've never seen anyone use.) Separators can also be omitted though that's apparently not recommended if quick human legibility is of concern. There's also YYYY-Wxx for week numbers.

[–] Ravi@feddit.de 11 points 2 years ago (1 children)

YYYY-MM-DD:HH:MM:SS+TZ

[–] Kata1yst@kbin.social 7 points 2 years ago

RFC3339! It's like ISO8601, but good!

[–] jlh@lemmy.jlh.name 10 points 2 years ago (1 children)

YYYY-MM-DDTHH:MM:SS.SSSSSSSSSZ

[–] Unaware7013@kbin.social 5 points 2 years ago

This, but all run together.

I write files/reports to disk a lot from scripts, so that's my preferred format.