import java.time.Instant;
import java.time.temporal.ChronoUnit;

public class Main {
	public static void main(String[] args) {
		// This is a sample Instant. In your case, it will be returned by
		// timeService.getDate().toInstant()
		Instant today = Instant.now();

		// This is a sample Instant after one day. In your case, it will be returned by
		// timeService.getDateAfter(1).toInstant()
		Instant tomorrow = today.plus(1, ChronoUnit.DAYS);

		long seconds = today.until(tomorrow, ChronoUnit.SECONDS);

		// In your case, you will use Assertions.assertEquals(86400, seconds);
		System.out.println(seconds);
	}
}