Get the time difference between two datetimes

Question

I know I can do anything and some more envolving Dates with momentjs. But embarrassingly, I'm having a hard time trying to do something that seems simple: geting the difference between 2 times.

Example:

var now  = "04/09/2013 15:00:00";
var then = "04/09/2013 14:20:30";

//expected result:
"00:39:30"

what I tried:

var now = moment("04/09/2013 15:00:00");
var then = moment("04/09/2013 14:20:30");

console.log(moment(moment.duration(now.diff(then))).format("hh:mm:ss"))
//outputs 10:39:30  

I do not understand what is that "10" there. I live in Brazil, so we are utc-0300 if that is relevant.

The result of moment.duration(now.diff(then)) is a duration with the correct internal values:

 days: 0
 hours: 0
 milliseconds: 0
 minutes: 39
 months: 0
 seconds: 30
 years: 0

So, I guess my question is: how to convert a momentjs Duration to a time interval? I sure can use

duration.get("hours") +":"+ duration.get("minutes") +:+ duration.get("seconds")

but i feel that there is something more elegant that I am completely missing.

update
looking closer, in the above example now is:

Tue Apr 09 2013 15:00:00 GMT-0300 (E. South America Standard Time)…}

and moment(moment.duration(now.diff(then))) is:

Wed Dec 31 1969 22:39:30 GMT-0200 (E. South America Daylight Time)…}

I am not sure why the second value is in Daylight Time (-0200)... but I am sure that i do not like dates :(

update 2

well, the value is -0200 probably because 31/12/1969 was a date where the daylight time was being used... so thats that.

Answer 1

This approach will work ONLY when the total duration is less than 24 hours:

var now  = "04/09/2013 15:00:00";
var then = "04/09/2013 14:20:30";

moment.utc(moment(now,"DD/MM/YYYY HH:mm:ss").diff(moment(then,"DD/MM/YYYY HH:mm:ss"))).format("HH:mm:ss")

// outputs: "00:39:30"

If you have 24 hours or more, the hours will reset to zero with the above approach, so it is not ideal.

If you want to get a valid response for durations of 24 hours or greater, then you'll have to do something like this instead:

var now  = "04/09/2013 15:00:00";
var then = "02/09/2013 14:20:30";

var ms = moment(now,"DD/MM/YYYY HH:mm:ss").diff(moment(then,"DD/MM/YYYY HH:mm:ss"));
var d = moment.duration(ms);
var s = Math.floor(d.asHours()) + moment.utc(ms).format(":mm:ss");

// outputs: "48:39:30"

Note that I'm using the utc time as a shortcut. You could pull out d.minutes() and d.seconds() separately, but you would also have to zeropad them.

This is necessary because the ability to format a duration objection is not currently in moment.js. It has been requested here. However, there is a third-party plugin called moment-duration-format that is specifically for this purpose:

var now  = "04/09/2013 15:00:00";
var then = "02/09/2013 14:20:30";

var ms = moment(now,"DD/MM/YYYY HH:mm:ss").diff(moment(then,"DD/MM/YYYY HH:mm:ss"));
var d = moment.duration(ms);
var s = d.format("hh:mm:ss");

// outputs: "48:39:30"

Answer 2

Your problem is in passing the result of moment.duration() back into moment() before formatting it; this results in moment() interpreting it as a time relative to the Unix epoch.

It doesn't give you exactly the format you're looking for, but

moment.duration(now.diff(then)).humanize()

would give you a useful format like "40 minutes". If you're really keen on that specific formatting, you'll have to build a new string yourself. A cheap way would be

[diff.asHours(), diff.minutes(), diff.seconds()].join(':')

where var diff = moment.duration(now.diff(then)). This doesn't give you the zero-padding on single digit values. For that, you might want to consider something like underscore.string - although it seems like a long way to go just for a few extra zeroes. :)