How to grab the last 12 months from cygwin "date" with a static time value

I've got this script

"$(date +%Y-%m-01) -$i months" +%Y-%m)-01"

that works great for getting the last 12 months from date, month by month. I want to have a static value for the time being used, so that instead of going back 12 months from the CURRENT TIME it is going back from a static time.

I'm using this with Github and I want to be consistent with the commits I sync to when I want to go back x months. How to specify time down to the second and use it with this script?

Solution

You could just use what git proves you: git log --since='X seconds ago', e.g. to list all commits in the last year (approximately 365*24*60*60=31536000 seconds)

$ git log --since='31536000 seconds ago'

You can give an upper bound with --until.

If you want to list all commits one year before SOME_DATE you can use date.

# the current time (NOW)
date +%s

# the time a SOME_DATE (e.g. 2011-01-01)
date +%s --date=2011-01-01

# one year before SOME_DATE is
#
#   31536000 + NOW - SOME_DATE
#
# (use bc for calculations)
SECONDS=$(echo 31536000 -  $(date +%s) + $(date +%s --date=2011-01-01) | bc)

# putting it all together:
# display all commits since one year before 2011-01-01 until 2011-01-01
git log --since="$(echo 31536000 + $(date +%s) - $(date +%s --date=2011-01-01)| bc) seconds ago" --before="$(echo $(date +%s) - $(date +%s --date=2011-01-01) | bc -l) seconds ago"