clock : Java Glossary

In a PC (Personal Computer) are two clocks, a more accurate clock calendar and a less accurate a tick counter. The tick counting clock is reset from the clock calendar every time you reboot. This is why your screen clock tends to be more accurate just after a reboot. You can reset both clocks from an highly accurate atomic clock. Unfortunately Microsoft and Linux/Unix people use the CMOS (Complementary Metal Oxide on Silicon) clock in incompatible ways. This can cause trouble on dual boot machines. Perhaps the easiest way to deal with this is to call w32tm.exe /resync in Vista, W2008, W7-32, W7-64, W8-32, W8-64, W2012, W10-32 and W10-64 to resync your clock indirectly from an atomic clock on the web on boot. You configue a more reliable time source with Control Panel ⇒ Date and Time ⇒ Internet Time ⇒ change settings ⇒ pool.ntp.org. Make sure you have your time zone also configured correctly with DST (Daylight Saving Time) correction on. w32tm.exe will only work after the W32Time service is started. On older Windows machines, you can use SetClock. Windows uses a less-accurate stripped down SNTP (Simple Network Time Protocol) protocol. You will get much more accurate time with full NTP (Network Time Protocol).

Installing Meinberg NTP software for Windows is very easy to set up. It does not require run as administer. It is very accurate.

Vista supplies Java with UTC (Coordinated Universal Time/Temps Universel Coordonné). It then uses its own time zone tables and DST information to convert to local time.

In W10-32 and W10-64 w32tm.exe will not work unless your run as administrator. You can do it by starting a command window with run as administor then running the bat file containing the w32tm.exe call.