How can i find HH:MM:SS difference between two UNIX times

Question

I have a Webhook listener that receives a unix timestamp value. This timestamp is my END time.

I would like to use the current unix timestamp and compare what HH:MM:SS are left until the end time.

I was reading this post: How can i find HH:MM:SS difference between two UNIX timestamps? and think it is very similar to my needs but needs a little tweaking.

Example:

Current time = unix now time
End time = unix time 
= How many HH:MM:SS remain before the time has ended

I was trying;

function timeDiff(EpochTime) {
    let msec = (new Date()).valueOf() - EpochTime * 1000;
    const hh = Math.floor(msec / 1000 / 60 / 60);
    msec -= hh * 1000 * 60 * 60;
    const mm = Math.floor(msec / 1000 / 60);
    msec -= mm * 1000 * 60;
    const ss = Math.floor(msec / 1000);
    msec -= ss * 1000;
    return `${mm}m ${ss}s`;
}

Thanks Magik

Answer 1

GNU awk is an option:

awk -v etim="2021 02 08 16 27 00" '{ print strftime("%c",mktime(etim)-strftime("%s"),1) }' <<< /dev/null

Pass the date/time as etim and the use GNU awk's strftime and mktime functions to print the difference in the passed date and now in the locale format. Change %c to what ever format is required.