How to compare LocalDateTime instances in kotlin - kotlin

Question

so I'm having a little problem with kotlin LocalDateTime
val now = CurrentDateTime
val someDate = someService.someLocalDateTime
I have two dates as you can see and I want to know if now is bigger than someDate or not.
and also I need to know if it's bigger, how much is bigger.
i can do it by checking year, month, day, minute and second like this:
if (now.year().toString() == someDate.year.toString())
but it's not a good way
any suggesstions would be welcome.

Answer 1

You can simply convert both dates in seconds and:
compare them to know which one is bigger
subtract them to know how much one is bigger than the other
an example would be
val now = CurrentDateTime.toEpochSeconds()
val someDate = someService.someLocalDateTime.toEpochSeconds();
if(now > someDate)
//someDate is in the past
else
//someDate is in the future or both dates are equal
val distance = now-someDate
hope this helps

Answer 2

The standard solution to compare two Date objects is by using the compareTo() function. It returns a value
= 0, if both dates are equal.
< 0, if date is before the specified date.
> 0, if date is after the specified date.
The following program demonstrates it:
import java.text.SimpleDateFormat
import java.util.*
fun main() {
val now = CurrentDateTime // "01/21/2023"
val someDate = someService.someLocalDateTime // "01/21/2020"
val sdf = SimpleDateFormat("MM/dd/yyyy")
val firstDate: Date = sdf.parse(now)
val secondDate: Date = sdf.parse(someDate)
val cmp = firstDate.compareTo(secondDate)
when {
cmp > 0 -> {
System.out.printf("%s is after %s", d1, d2)
}
cmp < 0 -> {
System.out.printf("%s is before %s", d1, d2)
}
else -> {
print("Both dates are equal")
}
}
}

Answer 3

Convert Kotlin LocalDateTime to Java LocalDateTime
To convert Kotlin LocalDateTime to Java LocalDateTime, you can make use of this function:
fun LocalDateTime.toJavaLocalDateTime(): LocalDateTime
Converts this kotlinx.datetime.LocalDateTime value to a java.time.LocalDateTime value.
And then you can choose to use the following method or other suggested method to compare the converted java.time.LocalDateTime.
Compare Java LocalDateTime
To compare LocalDateTime, you can use LocalDateTime's isAfter(), isBefore(), isEqual().
import java.time.LocalDateTime
fun main() {
val currentTime = LocalDateTime.now()
val ytdTime = LocalDateTime.now().minusDays(1)
println(currentTime.isAfter(ytdTime))
println(currentTime.isBefore(ytdTime))
println(currentTime.isEqual(ytdTime))
}
Output
true
false
false
To find the difference between LocalDateTime, you can use ChronoUnit:
import java.time.temporal.ChronoUnit
fun main() {
val currentTime = LocalDateTime.now()
val ytdTime = LocalDateTime.now().minusDays(1)
val secondDifference = ChronoUnit.SECONDS.between(ytdTime, currentTime)
val minutesDifference = ChronoUnit.MINUTES.between(ytdTime, currentTime)
val hourDifference = ChronoUnit.HOURS.between(ytdTime, currentTime)
println(secondDifference)
println(minutesDifference)
println(hourDifference)
}
Output
86399
1439
23