Sortable, readable and standard time format for logs

Question

Timestamp format in logs

Most log lines contain a timestamp and event description:

[When] [What]

e.g.:

[23/Jul/20         


        

Answer 1

The unix date command has such an option. Use

date -Iseconds

or

date -Ins

The manpage says:

   -I[FMT], --iso-8601[=FMT]
          output  date/time  in  ISO  8601  format.   FMT='date' for date only (the default),
          'hours', 'minutes', 'seconds', or 'ns' for date and time to  the  indicated  preci‐
          sion.  Example: 2006-08-14T02:34:56-0600

Answer 2

@J.F. Sebestian - Thanks for your comment.

After some research I chose RFC 3339 / ISO 8601 in UTC, e.g.:

date -u "+[%Y-%m-%d %H:%M:%S%z (%Z)]"       # Space separated with tz abbreviation
[2013-07-31 23:56:34+0000 (UTC)]                   

date -u "+[%Y-%m-%d %H:%M:%S.%N %z (%Z)]"  # Space separated with nanoseconds and tz abbreviation
[2013-07-31 23:56:34.812572000 +0000 (UTC)]

Features:

• Sortable (Most significant date item is on the left)
• Readable
• Unambiguous, time zone clearly stated
• Delimited by [,], useful for regexing the date away
• Easily parsable
• Accurate: uses nanoseconds (might be practically milliseconds on some machines, which is good enough)

I've also created a nice github project that helps with date formatting - feel free to take a look and suggest your own formats!