TimeZoneTest

TimeZoneTest.java

import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.util.TimeZone;
import java.util.concurrent.TimeUnit;

public class TimeZoneTest {

	// https://www.worldtimebuddy.com/?pl=1&lid=2643743,3448439,3530597&h=2643743
	public static void main(String[] args) {
		String date = "2019-09-30T05:00:00Z";
		String timezone = "America/Mexico_City";
		Instant instant = Instant.parse(date);
		LocalDateTime tzo = LocalDateTime.ofInstant(instant, ZoneId.of(timezone));
		LocalDateTime dateCalculated = tzo.minusDays(1);
		System.out.println("Timezone:    " + timezone);
		System.out.println("Cron UTC:    " + date);
		System.out.println("Current tz:  " + tzo);
		System.out.println("Will run in: " + dateCalculated.toLocalDate());

		System.out.println("\nTimezone Availables:");
		for (String id : TimeZone.getAvailableIDs()) {
			System.out.println(displayTimeZone(TimeZone.getTimeZone(id)));
		}
	}

	private static String displayTimeZone(TimeZone tz) {
		long hours = TimeUnit.MILLISECONDS.toHours(tz.getRawOffset());
		long minutes = TimeUnit.MILLISECONDS.toMinutes(tz.getRawOffset()) - TimeUnit.HOURS.toMinutes(hours);
		minutes = Math.abs(minutes);
		if (hours > 0) {
			return String.format("(GMT+%d:%02d) %s", hours, minutes, tz.getID());
		}
		return String.format("(GMT%d:%02d) %s", hours, minutes, tz.getID());
	}
}