AddOriginal adds the name of a new entry in table of original TZs.

AddReplicas adds a new list of entries in the preplicas' table.

AddZones creates a new table and adds a list of zones.

GetOriginalByName retrieves ID for a named origial TZ.

GetZones retrieves available zones for specified timezone.

UpdateOriginal updates data of an existing entry in original timezones table.

UpdateReplica updates the origial timezone linked to the specified replica.

Original defines a unique timezone.

Replica defines a link to some timezone.

Zone defines a zone within a timezone.