DurationToHumanReadableString.kt

val units = listOf(
    ChronoUnit.MILLENNIA,
    ChronoUnit.CENTURIES,
    ChronoUnit.DECADES,
    ChronoUnit.YEARS,
    ChronoUnit.MONTHS,
    ChronoUnit.WEEKS,
    ChronoUnit.DAYS,
    ChronoUnit.HOURS,
    ChronoUnit.MINUTES,
    ChronoUnit.SECONDS
)

fun main() {
    println(durationToHumanReadableString((Duration.ofHours(12) + Duration.ofMinutes(30)).toMillis())) // 12 Hours 30 Minutes
    println(durationToHumanReadableString(Duration.ofDays(1000000).toMillis())) // 2 Millennia 7 Centuries 3 Decades 7 Years 10 Months 3 Weeks 5 Days 21 Hours 48 Minutes 36 Seconds
    println(durationToHumanReadableString((Duration.ofDays(365) + Duration.ofDays(183)).toMillis())) // 1 Years 6 Months 3 Hours 16 Minutes 12 Seconds
}

fun durationToHumanReadableString(durationInMillis: Long): String {
    units.forEach { unit ->
        if (durationInMillis >= unit.duration.toMillis()) {
            val durationValue = durationInMillis / unit.duration.toMillis()
            val remainder = durationInMillis.rem(unit.duration.toMillis())
            val remainderString = if (remainder != 0L) {
                " ${durationToHumanReadableString(remainder)}"
            } else {
                ""
            }
            return "$durationValue $unit$remainderString"
        }
    }

    return ""
}