How to get the difference betweeen two dates (jetpack compose/kotlin)? - kotlin

Question

I have to calculate how many days are left between the date selected by the user through a DatePicker and the current date
I was trying to write something like this:
val simpleDate = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'")
val date = simpleDate.parse(event!!.date!!)
val diff = Duration.between(LocalDate.now(), date.toInstant())
val leftDays = diff.toDays()

Answer 1

Your mix of outdated (SimpleDateFormat, 'Date') and modern (LocalDate) APIs is not optimal, I think:
I would use plain java.time here, because…
you can obviously use it in your application
it has a specific class for datetime Strings of the pattern you have shown in your question: an OffsetDateTime and
there's a java.time.Duration which you have tried to use
Here's an example:
fun main(args: Array<String>) {
// example input, some future datetime
val input = "2022-12-24T13:22:51.837Z"
// parse that future datetime
val offsetDateTime = OffsetDateTime.parse(input)
// build up a duration between the input and now, use the same class
val duration = Duration.between(OffsetDateTime.now(), offsetDateTime)
// get the difference in full days
val days = duration.toDays()
// print the result as "days left"
println("$days days left")
}
Output:
110 days left
If you don't receive a datetime but a date without time (just day of month, month of year and year), then use a LocalDate and calculate the ChronoUnit.DAYS.between(today, futureDate)
fun main(args: Array<String>) {
// example input, some future date
val input = "2022-12-24"
// parse that
val futureDate = LocalDate.parse(input)
// get the difference in full days
val days = ChronoUnit.DAYS.between(LocalDate.now(), futureDate)
// print the result
println("$days days left")
}
Output (again):
110 days left

Answer 2

Try below code -
val previousTimeDouble: Double = previousTime.toDouble()
val nowTimeDouble: Double = System.currentTimeMillis().toDouble()
val dateNowString: String = dateNow.toString();
val time: Long = (nowTimeDouble - previousTimeDouble).toLong()
val difference: String= differenceBetweenTwoTimes(time)
Log.d("difference", difference)
Function for converting time difference into units -
fun differenceBetweenTwoTimes(time: Long): String {
var x: Long = time / 1000
var seconds = x % 60
x /= 60
var minutes = x % 60
x /= 60
var hours = (x % 24).toInt()
x /= 24
var days = x
return String.format("%02d:%02d:%02d", hours, minutes, seconds)
}