import java.time.Instant;
import java.time.LocalDate;
import java.time.LocalTime;
import java.time.ZoneId;
import java.time.ZonedDateTime;

public class Main {
	public static void main(String[] args) {
		String strDate = "2021-11-25";
		String strTime = "15:20";
		ZonedDateTime zdt = ZonedDateTime.of(LocalDate.parse(strDate), LocalTime.parse(strTime),
												ZoneId.systemDefault());
		// Alternatively
		// ZonedDateTime zdt = ZonedDateTime.of(LocalDateTime.of(LocalDate.parse(strDate), LocalTime.parse(strTime)),
		//											ZoneId.systemDefault());
		
		Instant instant = zdt.toInstant();
		System.out.println(instant);
	}
}