For countries such as Indonesia having 3 different time zones, is there a way to tag each of these timezones for each region of Indonesia?
in the OSM wiki I found http://wiki.openstreetmap.org/wiki/Key:timezone
But I remeber some voices that say: OSM is not the right place to store timezones and other “not so concrete” objects …
see for example https://help.openstreetmap.org/questions/40059/are-radio-coverage-areas-as-polygons-of-interest-or-allowed-on-osm
So before you start adding any timezone elements to the main OSM database, start a detailed communication on any appropriate OSM channel first.