Understanding the Etc/GMT time zone

royalghost picture royalghost · Sep 5, 2011 · Viewed 33.2k times · Source

What is the rationale behind Apple using Etc/GMT timezone when they return the receipt from the App Store for auto-renewable subscriptions.

What exactly is the Etc/GMT time zone? Does the Java SDK understand this time zone? Or do I have to use other third-party libraries like Joda-Time?

Answer

David Peden picture David Peden · Jan 11, 2014

Etc/GMT is not strictly the same thing as UTC or GMT. They represent the same instant in time only when the offset is 0. In all other cases, they are quite different.

Apple explains the designation here.

A quote directly from the link gives an example:

We use POSIX-style signs in the Zone names and the output abbreviations, even though this is the opposite of what many people expect. POSIX has positive signs west of Greenwich, but many people expect positive signs east of Greenwich. For example, TZ='Etc/GMT+4' uses the abbreviation "GMT+4" and corresponds to 4 hours behind UTC (i.e. west of Greenwich) even though many people would expect it to mean 4 hours ahead of UTC (i.e. east of Greenwich).