import java.time.Instant;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;

public class Main {
	public static void main(String[] args) {
		String strDate = "2021-11-25";
		String strTime = "15:20";
		DateTimeFormatter dtf = DateTimeFormatter.ISO_LOCAL_DATE_TIME.withZone(ZoneId.systemDefault());
		ZonedDateTime zdt = ZonedDateTime.parse(strDate + "T" + strTime, dtf);
		Instant instant = zdt.toInstant();
		System.out.println(instant);
	}
}