Get milliseconds until midnight

I'm creating an Android widget that I want to update every night at midnight. I am using an AlarmManager and I need to find out how many milliseconds are left from the current time until midnight. Here's my code:

AlarmManager mAlarmManager = (AlarmManager)context.getSystemService(android.content.Context.ALARM_SERVICE);
mAlarmManager.set(AlarmManager.ELAPSED_REALTIME, millisecondsUntilMidnight, mSrvcPendingingIntent);

How can I calculate how many milliseconds are left until midnight?

Thank you in advance.