This tool helps me keeping track of my gleitende Arbeitszeit (means: flextime) in my Excel time sheets.
It's very easy to install and use (assuming you use the same sheet as I and you store it in the same directory as I):
# install
$ go get github.com/5nord/glaz/cmd/glaz
# check-in
$ glaz in
# check-out
$ glaz out
# get state
$ glaz