NITZ

[2] NITZ has been an optional part of the official GSM standard since phase 2+ release 96.

In terms of standards and other timing or network access protocols such as NTP or CDMA2000, the quality and enforcement of NITZ is weak.

This standard allows the network to "transfer its current identity, universal time, DST and LTZ"[1] but each is optional, and support across RAN vendor and operator varies.

This presents a problem for device manufacturers, who are required to maintain a complex time zone database, rather than rely on the network operator.

Most modern handsets have their own internal time zone software and will automatically perform a daylight saving advance.