When launching an Android emulator from a snapshot, the date can be slow to update, if at all. This can cause problems with date-dependent functionality of your apps e.g. GCM registrations can fail if the device’s date is way out. Of course you can set the date via the GUI, but quicker than that is setting it through ADB in the command line.
The basic syntax is;
adb shell date -s "yyyymmdd.[[[hh]mm]ss]"
so, just setting the date would be;
$ ./adb shell date -s "20130405"
and with more than one device running
$ ./adb -s emulator-5556 shell date -s "20130405"