Parts of the historical time zone database

The historical time zone database is sourced from the public “Olson Time Zone Database,” and updated (synchronized to it) upon each NiagaraAX build. It is implemented using a “timezones.jar” file that contains histories of changed rules for any so-affected timezones, along with changes to the NRE (Niagara Runtime Environment) that support this new method.

There are 2 associated files with historical time zones in an AX-3.3 or later host’s !lib folder, described as follows:

timezones.jar : The time zone database, in Java archive format. Contains a collection of binary files, one representing each time zone. Upon each build of NiagaraAX, this timezones.jar file is updated (synchronized) to the Olson Time Zone Database to maintain historical accuracy.
system.properties : The file responsible for loading various system settings at NRE (Niagara Runtime Environment) boot time. This file now contains 2 keys pertaining to historical time zones:
- niagara.timezone.dbCache : The maximum number of zones to remain cached in memory when querying the database for a particular zone. This caching is done in an “LRU” fashion, vs. hitting the database repeatedly for the same zones. This method provides performance gains.
- niagara.timezone.eraTolerance : The number of milliseconds to wait before loading a new historical time zone era. The higher the number, the better the performance (yet lower the accuracy). The reverse is true for higher numbers

Please note that time zones in this database are not user editable, unlike with the earlier timezones.xml database.