How to get day of the week of GMT using kotlin?

Question

For EXAMPLE, current UTC time is:

17:14:24 UTC Friday, 5 November 2021

I want to get the result "6" (Sunday = 1 => Friday = 6)

Answer 1

Using kotlinx.datetime (which is multiplatform):

import kotlinx.datetime.DayOfWeek
import kotlinx.datetime.Instant
import kotlinx.datetime.TimeZone
import kotlinx.datetime.isoDayNumber
import kotlinx.datetime.toLocalDateTime

public val DayOfWeek.dayNumberStartingFromSunday: Int
    get() = when (this) {
        DayOfWeek.SUNDAY -> 1
        else -> isoDayNumber + 1
    }

fun main() {
//    val now: Instant = Clock.System.now()
    val now = Instant.parse("2021-11-05T17:14:24Z")
    val datetimeInUtc = now.toLocalDateTime(TimeZone.UTC)
    val dayNumberStartingFromSunday = datetimeInUtc.dayOfWeek.dayNumberStartingFromSunday
    println(dayNumberStartingFromSunday) // 6
}