Pega Platform uses the time zones provided by the JVM on which it runs. The JVM typically uses data provided by the Olson TZ database. Details on this database are available from https://www.iana.org/time-zones.
Note: Daylight savings time rules are supplied by Java JDK vendors. In a multinode system, it is important that the same rules are installed on each node. For details of vendor JDK support of daylight savings time and downloads, see the Oracle knowledge base.