Java tutorial
import java.time.LocalDateTime; import java.time.temporal.TemporalAdjusters; public class Main { public static void main(String[] args) { LocalDateTime a = LocalDateTime.of(2014, 6, 30, 12, 01); LocalDateTime t = a.with(TemporalAdjusters.firstDayOfMonth()); System.out.println(t); } }