Question

In my Application I am displaying some info to the users according to the user’s TimeZone.
I am allowing the users to select different cities in the world and to get the required info. By default I will get the TimeZone of the user from their Device using

                `TimeZone myTZ = TimeZone.getDefault();`

And once the user changes the TimeZone , I am saving it in preferences. No problem in storing and retrieving the values from the preferences.

When another TimeZone is selected I set that TimeZone as default TimeZone using

       `TimeZone.setDefault(TimeZone.getTimeZone("my_timezone"));`

when I print the TimeZone in the Log I am getting the TimeZone value as I set it. But when I use that TimeZone in my calculations I am getting previous TimeZone Value.

So I think the problem is the TimeZone is not changing , I want the user to set the selected TimeZone as their default TimeZone in their device. How shall I do this. What is the mistake I am doing?

Getting stuck in this for three days. Any suggestions to get out from this? Quick suggestion will helps me a lot. Thanks in Advance!!

Answer 1

As per documentation for TimeZone.setDefault(...) –

Overrides the default time zone for the current process only.

Warning: avoid using this method to use a custom time zone in your
process. This value may be cleared or overwritten at any time, which
can cause unexpected behavior. Instead, manually supply a custom time
zone as needed.

Apparently to change timezone through code you have to use AlarmManager. See the discussion here.

AlarmManager alarm = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
alarm.setTimeZone(timezone);

It requires this permission to be set in the manifest

<uses-permission  android:name="android.permission.SET_TIME_ZONE"></uses-permission>