I get date as string from backend and now at first...

# getting-started

[Jasmin Fajkic]

I get date as string from backend and now at first I need to convert it to date time and then to compare this date and current date difference in years, months, weeks, days, minutes and seconds. In JS I can do this easily with moment JS like this

function extractTime(time) {
  return {
    seconds: moment().diff(time, 'seconds'),
    minutes: moment().diff(time, 'minutes'),
    hours: moment().diff(time, 'hours'),
    days: moment().diff(time, 'days'),
    weeks: moment().diff(time, 'weeks'),
    months: moment().diff(time, 'months'),
    years: moment().diff(time, 'years'),
  };
}

Is there something similar in Kotlin that I can achieve same result?

[mkrussel]

You can get the duration of time passed between two Instants as a Duration.

https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.time/-duration/

But that only goes up to days.

Does not support weeks, months, or years becomes the time include in that varies.

To do what you want you would probably need to convert to a LocalDateTime and then just subtract the different parts handling the overflow behavior. Also need to beware that multiple LocalDateTime in the same location could represent different Instants because of how time jumps around due to day light savings time.

[Michael de Kaste]

Things like weeks, months and years are nonsensical when looking at a duration so at least that makes sense. But you can make something comparable in Kotlin pretty easily with your JS example:

fun extractTime(time: LocalDateTime) = ChronoUnit
    .values()
    .dropLast(1) // 'FOREVER' isn't a valid difference
    .associateWith { time.until(LocalDateTime.now(), it) }

This results into a map that looks like this:

{Nanos=939897175910792688, Micros=939897175913782, Millis=939897175913, Seconds=939897175, Minutes=15664952, Hours=261082, HalfDays=21756, Days=10878, Weeks=1554, Months=357, Years=29, Decades=2, Centuries=0, Millennia=0, Eras=0}

You can manually check the diffs just like you did in your JS example too

[Michael de Kaste]

although I would ofcourse not use LocalDateTime.now() every time for the different call, not even in the 'seconds' example since time elapses per operation, but you get the gist

[phldavies]

you could of course use fun extractTime(time: LocalDateTime, since: LocalDateTime = LocalDateTime.now()) = … to handle both cases neatly - allowing for a consistent delta for all chronounits and you can pass in a specific time for since when mapping over multiple dates

[ilya.gorbunov]

With kotlinx.datetime you can express two moments as Instant values and then use Instant.periodUntil(Instant, TimeZone) returning DateTimePeriod type which provides components of period from years to nanoseconds.