dayOfYear

import kotlinx.datetime.*
import kotlinx.datetime.format.*
import kotlin.test.*

fun main() { 
   //sampleStart 
   // Using day-of-year in a custom format
val format = LocalDate.Format {
    year(); dayOfYear()
}
check(format.format(LocalDate(2021, 2, 13)) == "2021044")
check(format.parse("2021044") == LocalDate(2021, 2, 13)) 
   //sampleEnd
}