How to change Git log date formats

The others are (from git help log):

--date=(relative|local|default|iso|rfc|short|raw)
  Only takes effect for dates shown in human-readable format,
  such as when using "--pretty".  log.date config variable
  sets a default value for log command’s --date option.

--date=relative shows dates relative to the current time, e.g. "2 hours ago".

--date=local shows timestamps in user’s local timezone.

--date=iso (or --date=iso8601) shows timestamps in ISO 8601 format.

--date=rfc (or --date=rfc2822) shows timestamps in RFC 2822 format,
  often found in E-mail messages.

--date=short shows only date but not time, in YYYY-MM-DD format.

--date=raw shows the date in the internal raw git format %s %z format.

--date=default shows timestamps in the original timezone
  (either committer’s or author’s).

There is no built-in way that I know of to create a custom format, but you can do some shell magic.

timestamp=`git log -n1 --format="%at"`
my_date=`perl -e "print scalar localtime ($timestamp)"`
git log -n1 --pretty=format:"Blah-blah $my_date"

The first step here gets you a millisecond timestamp. You can change the second line to format that timestamp however you want. This example gives you something similar to --date=local, with a padded day.

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And if you want permanent effect without typing this every time, try

git config log.date iso 

Or, for effect on all your git usage with this account

git config --global log.date iso

In addition to --date=(relative|local|default|iso|iso-strict|rfc|short|raw), as others have mentioned, you can also use a custom log date format with

--date=format:'%Y-%m-%d %H:%M:%S'       # committer's timezone
--date=format-local:'%Y-%m-%d %H:%M:%S' # current user's timezone

This outputs something like 2016-01-13 11:32:13.

NOTE: If you take a look at the commit linked to below, I believe you'll need at least Git v2.6.0-rc0 for this to work.

In a full command it would be something like:

git config --global alias.lg "log --graph --decorate -30 --all --topo-order --date=format-local:'%Y-%m-%d %H:%M:%S' --pretty=format:'%C(cyan)%h%Creset %C(black bold)%ad%Creset%C(auto)%d %s'"

I haven't been able to find this in documentation anywhere (if someone knows where to find it, please comment) so I originally found the placeholders by trial and error.

In my search for documentation on this I found a commit to Git itself that indicates the format is fed directly to strftime. Looking up strftime (here or here) the placeholders I found match the placeholders listed.

The placeholders include:

%a      Abbreviated weekday name
%A      Full weekday name
%b      Abbreviated month name
%B      Full month name
%c      Date and time representation appropriate for locale
%d      Day of month as decimal number (01 – 31)
%H      Hour in 24-hour format (00 – 23)
%I      Hour in 12-hour format (01 – 12)
%j      Day of year as decimal number (001 – 366)
%m      Month as decimal number (01 – 12)
%M      Minute as decimal number (00 – 59)
%p      Current locale's A.M./P.M. indicator for 12-hour clock
%S      Second as decimal number (00 – 59)
%U      Week of year as decimal number, with Sunday as first day of week (00 – 53)
%w      Weekday as decimal number (0 – 6; Sunday is 0)
%W      Week of year as decimal number, with Monday as first day of week (00 – 53)
%x      Date representation for current locale
%X      Time representation for current locale
%y      Year without century, as decimal number (00 – 99)
%Y      Year with century, as decimal number
%z, %Z  Either the time-zone name or time zone abbreviation, depending on registry settings
%%      Percent sign