Info about tz database data storage in Wikipedia can be found at Template:Time zone/doc#tz database. From zone.tab:
# 2. Latitude and longitude of the zone's principal location # in ISO 6709 sign-degrees-minutes-seconds format, # either +-DDMM+-DDDMM or +-DDMMSS+-DDDMMSS, # first latitude (+ is north), then longitude (+ is east).