The clock accuracy on Windows seems to have changed lately. I remember it being very accurate since Windows 7 (1 ms resolution), and now the time hops in steps of 15 to 16 ms. I noticed due to some (albeit poorly written) unit tests failing (tests checked that some time elapsed between writing and reading records).
This affects following implementations:
System.currentTimeMillis()LocalTime.now()LocalDateTime.now()ZonedDateTime.now()
I'm well aware that elapsed time is to be measured using System.nanoTime() deltas, but I'm wondering nevertheless if I missed something that changed back the clock resolution to 15-16ms.
Environment:
- Windows 10 version 1709
- JRE/JDK 1.8.0_171-b11 (64-bit)
Did anyone notice this as well? What could be the reason for this resolution change?
EDIT:
Test code to check this behaviour (see output: time changes and number of samples before change)
@Test public void testCurrentTimeMillis() { test(() -> System.currentTimeMillis()); } @Test public void testNanoTime() { test(() -> System.nanoTime()); } @Test public void testLocalTime() { test(() -> LocalTime.now()); } @Test public void testLocalDateTime() { test(() -> LocalDateTime.now()); } @Test public void testZonedDateTime() { test(() -> ZonedDateTime.now()); } private <T> void test(Supplier<T> timeSupplier) { int samples = 20; String lastTimeString = null; int count = 0; while (samples > 0) { count++; String timeString = timeSupplier.get().toString(); if (!timeString.equals(lastTimeString)) { System.out.println(timeString + " (" + count + ")"); lastTimeString = timeString; count = 0; samples--; } } } 
