NTP operates using UTC (Coordinated Universal Time) rather than local time. UTC is the global time standard that doesn’t change for daylight saving time (DST) and is used as the reference for all time zones worldwide.
UTC time is very similar, but not quite exactly the same as GMT (Greenwich Mean Time). It is the same all around the world and is unaffected by time zones or daylight saving time.
By utilizing UTC, NTP knows nothing of time zones and daylight saving. It obtains accurate UTC from GPS or LF radio time references or from other NTP servers. It then provides UTC to network time clients for synchronization purposes.
The adjustment to local time is a function of the client. For instance in Windows, the ‘Date and Time Properties’ applet tells Windows what offset should be applied to UTC time in order to provide local time. It adjusts its underlying UTC clock according to the time zone and daylight saving properties selected, in order to provide local time. Linux and most other operating systems work in a similar manner.
By using UTC, any client anywhere in the world can synchronize to a NTP server anywhere else in the world without being concerned with time zone and daylight saving offsets. Therefore, NTP servers display UTC time – with no offset or adjustment for time zone and daylight saving.