Parsing a date/time (converting it from a string)
jq 'strptime("%Y-%m-%dT%H:%M:%SZ")|mktime' <<< \"$(gdate -u +'%Y-%m-%dT%H:%M:%SZ' -d "13:30")\"
f='%Y-%m-%d_%H:%M'; jq "strptime(\"$f\")|mktime" <<< \"$(gdate -u +$f -d "13:30")\"
!! > tmp/date
Learning jq through a timesheet app
jq 'strptime("%Y-%m-%dT%H:%M:%SZ")|mktime' <<< \"$(gdate -u +'%Y-%m-%dT%H:%M:%SZ' -d "13:30")\"
f='%Y-%m-%d_%H:%M'; jq "strptime(\"$f\")|mktime" <<< \"$(gdate -u +$f -d "13:30")\"
!! > tmp/date