public static String utcDateAsString(Instant instant) {
        DateTimeFormatter formatter = DateTimeFormatter.ISO_LOCAL_DATE.withZone(ZoneOffset.UTC);
        return formatter.format(instant);
    }
@Test
    public void testUtcDateAsString() {

        assertEquals(
            "1970-01-01",
            TimeUtils.utcDateAsString(Instant.EPOCH)
        );

        assertEquals(
            "1970-01-03",
            TimeUtils.utcDateAsString(Instant.EPOCH.plus(2, ChronoUnit.DAYS))
        );
    }