toEpochMilliseconds

import kotlin.test.*
import kotlin.time.*
import kotlin.time.Duration.Companion.hours
import kotlin.time.Duration.Companion.nanoseconds
import kotlin.time.Duration.Companion.seconds

fun main() { 
   //sampleStart 
   val currentInstant = Clock.System.now()
// The number of whole milliseconds that have passed since the Unix epoch.
println(currentInstant.toEpochMilliseconds())

// When an Instant is created with fromEpochMilliseconds,
// toEpochMilliseconds will return the exact value provided.
val instant1 = Instant.fromEpochMilliseconds(0)
println(instant1.toEpochMilliseconds()) // 0
val instant2 = Instant.fromEpochMilliseconds(1_000_000_000_123)
println(instant2.toEpochMilliseconds()) // 1000000000123

// Any fractional part of a millisecond is rounded toward zero to the whole number of milliseconds.
val instant3 = Instant.fromEpochSeconds(1_000_000_000, nanosecondAdjustment = 123_999_999)
println(instant3.toEpochMilliseconds()) // 1000000000123 
   //sampleEnd
}