Last update was done 8 months ago (to 2015a database, see MDL-49073). Going to update to tzdata2015g.tar.gz
Instructions:
Use https://gist.github.com/jethac/ee03aff52176fb7cc9fe to generate a file from the timezones data in iana.org, rename it as olson.txt
1) Put the olson.txt file into dataroot/temp/olson.txt
2) Go to Admin -> Location -> Update timezones and confirm
3) Data will be loaded, replacing existing one
4) Generate CSV file from phpMyAdmin (commas as field separators, non-quoted values, unix line feeds and first line as field names)
5) Put it into /lib/timezone.txt
6) Commit
Note1: Current timezone.txt format is compatible only with Moodle 1.8 and upwards.
Note2: We'll be spreading this change to 2.7 and 2.8 as this is not needed in 2.9 onwards after MDL-49684 changes
Ciao