The Java-sourced time zone database has a “historical perspective,” where a history of changes for applicable time zones are
stored. Thus, multiple definitions for a time zone may exist, including past definitions as well as its current definition.
This allows display of a station’s timestamped data (histories and alarms) collected in time zones under “prior rules” (typically
DST-related) to display with the original (and correct) collected time.
NOTE: On all
Niagara 4 JACE controller platforms, the Java-sourced time zone database is historically accurate only back to year 2010. Any pre-2010 historical
data is displayed using 2010 rules. This was done to improve Java heap usage on these platforms.
However, note the Java-sourced time zone database on Windows
Niagara 4 platforms extends further back, for example, to year 1995.
In
Workbench, select to navigate the Java time zone database, where you can explore DST rules for any timezone. If a local station is running
on the same host (
Supervisor), this is time zone database that is utilized. For more information, see “Time Zone Database Tool” in Getting Started with Niagara.