A standard for timestamps.
It is roughly yyyy-mm-ddTHH:MM:SSZ
, where
-
yyyy is the 4-digit year
-
mm is the 2-digit month
-
dd is the 2-digit day
-
HH is the hour
-
MM is the minute
-
SS is the second
-
and Z is the offset from UTC.
The offset from UTC is roughly written in this format:
-
Z
stands for UTC. It's also referred to as Zulu time. -
Otherwise, it's either
+HH:MM
or-HH:MM
.
Omitting the colon in the UTC offset
I tend to omit the colon in the UTC offset, but I'm not sure if this actually conforms to the standard.
Emacs does this by default:
For example, to produce full ISO 8601 format, use "%FT%T%z".
— Emacs docstring for
format-time-string
(format-time-string "%FT%T%z") ; => 2021-06-07T20:21:18+0900
Shortened version
As far as I remember, there is also a shortened version defined in the standard, which removes all dashes and colons.
20210607T000000+0900