How to compare dates formatted as `Tue Aug 30 12:01:37 GMT 2022` in BusyBox/Alpine

In shell (no bash because of Alpine) using BusyBox, how can I compare two dates both formatted as Tue Aug 30 12:01:37 GMT 2022?

I want to know which one comes first. date doesn't support this input format. I'm only interested in whole days. The time isn't interesting for me. So two dates on the same day but a different time are equal to me.

Of course I could put all the names of the months in a lookup table and use the index of the month as its integer value (to be able to compare) but I have the feeling I shouldn't be the one programming that out...


/opt/scripts $ a="Tue Aug 30 12:01:37 GMT 2022"
/opt/scripts $ date -d "$a" +%s
date: invalid date 'Tue Aug 30 12:01:37 GMT 2022'
/opt/scripts $ date --help
BusyBox v1.34.1 (2022-04-04 10:19:27 UTC) multi-call binary.

Usage: date [OPTIONS] [+FMT] [[-s] TIME]

Display time (using +FMT), or set time

        -u              Work in UTC (don't convert to local time)
        [-s] TIME       Set time to TIME
        -d TIME         Display TIME, not 'now'
        -D FMT          FMT (strptime format) for -s/-d TIME conversion
        -r FILE         Display last modification time of FILE
        -R              Output RFC-2822 date
        -I[SPEC]        Output ISO-8601 date
                        SPEC=date (default), hours, minutes, seconds or ns

Recognized TIME formats:
        YYYY-MM-DD hh:mm[:ss]
        'date TIME' form accepts MMDDhhmm[[YY]YY][.ss] instead
/opt/scripts $


  • Install dateutils . Use strptime to convert the date to seconds. Compare seconds.

    apk add dateutils
    a=$(strptime -f %s -i "%a %b %d %T %Z %Y" "Tue Aug 30 12:01:37 GMT 2022")
    b=$(strptime -f %s -i "%a %b %d %T %Z %Y" "Tue Aug 30 12:01:38 GMT 2022")
    [ "$a" -lt "$b")