How to check if the current time is after or before a certain time in kotlin

Question

I am trying to check if the current time (hours and minute) is after or before a certain time, how can I do it in kotlin

Answer 1

If you have a LocalDateTime or similar, you can extract the MINUTE_OF_DAY (which is basically hours + minutes) to compare the time and ignoring the rest, e.g.:

val now = LocalDateTime.now()
val dateToCompare : LocalDateTime = TODO()

val minutesOfDayNow = now.get(ChronoField.MINUTE_OF_DAY)
val minutesOfDayToCompare = dateToCompare.get(ChronoField.MINUTE_OF_DAY)

when {
  minutesOfDayNow == minutesOfDayToCompare -> // same hour and minute of day
  minutesOfDayNow > minutesOfDayToCompare -> // hours and minutes now are after the time to compare (only in regards to hours and minutes... not day/month/year or whatever)
  minutesOfDayNow < minutesOfDayToCompare -> // hours and minutes now are before the time to compare... same conditions apply
}

If you instead have a Date you may be interested in transforming it to an instance of a java.time-type before, e.g.:

fun Date.minutesOfDay() = toInstant().atZone(ZoneId.systemDefault()).get(ChronoField.MINUTE_OF_DAY)

val now = Date()
val dateToCompare : Date = TODO()

if (now.minutesOfDay() > dateToCompare.minutesOfDay()) // ...etc. pp.

Finally if you want to use Calendar just be sure to compare only the things you are interested in, i.e. the hours and minutes and nothing more, e.g.:

val now = Calendar.getInstance()
val nowInMinutes = now[Calendar.HOUR_OF_DAY] * 60 + now[Calendar.MINUTE]

val dateInMinutesToCompare = hours * 60 + minutes

when {
  nowInMinutes == dateInMinutesToCompare -> // equal
  nowInMinutes > dateInMinutesToCompare -> // now after given time
  else -> // now before given time
}

Answer 2

You must first specify now and then the future time in two variables for comparison. You can then compare them with isBefore and isAfter to determine true/false on either.

val timeNow = LocalTime.now()
val timeTo = LocalTime.parse("15:00:00")
timeTo.isBefore(timeNow) // boolean for `before`
timeTo.isAfter(timeNow) // boolean for `after`