Time Zones

Platform configuration of the Niagara host includes specifying its time zone. This affects both real time clock accuracy used in station control, and also how timestamps appear in items like histories and alarms.

A time zone is a region in the world that uses the same standard time, often referred to as the local time. There are many different time zones, owing to the combinations of geographic locations and political/cultural differences. Time zones calculate their local time as an offset from UTC (Coordinated Universal Time). In addition, many time zones apply DST (Daylight Saving Time).

The Java-sourced time zone database has an 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. The Time Zone Database Tool provides access to the historical time zone database on the local host.

This facilitates the display of a station’s timestamped data (histories and alarms) collected in time zones under prior rules (typically DST-related). These timestamps display with their original (and correct) collected time.

Note: On all Niagara 4 controller platforms, the Java-sourced time zone database is historically accurate only back to the year 2010. Any pre-2010 historical data are displayed using 2010 rules. This was done to improve Java heap usage on these platforms.

However, the Java-sourced time zone database on Windows Niagara 4 platforms extends further back, for example, to the year 1995.

In Workbench, select Tools > Time Zone Database Tool 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 the time zone database used. For more information, refer to the Getting Started with Niagara.