Question

So i save the time-stamp as a Date object and a timezone as a TimeZone object.

Now i want to make a function that takes a Date object and a TimeZone object as argument and returns a Date object adjusted using the time-stamp.

For example :

Input :

Date    TimeZone 

12:00   Moscow Standard Time (UTC+3)

Output :

Date 

3:00    

Edit:
Removed Note about Calendar

Answer 1

A java.util.Date is an absolute point in time. 0900 hours UTC and 1200 hours UTC+3 are the exact same java.util.Date object. There is no ‘adjustment’ to be made to it in order to represent one or the other.

To get the human readable representation accounting for a particular timezone, you can set a timezone on a DateFormat object.

DateFormat format = new SimpleDateFormat("HH:mm");
format.setTimeZone(TimeZone.getTimeZone("UTC+3"));
String time = format.format(yourDate);

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Solution for the question posed in comment:

Calendar cal1 = Calendar.getInstance(TimeZone.getTimeZone("UTC+3"));
cal1.setTime(yourDate);
Calendar cal2 = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
cal2.clear();
cal2.set(Calendar.YEAR, cal1.get(Calendar.YEAR));
cal2.set(Calendar.MONTH, cal1.get(Calendar.MONTH));
cal2.set(Calendar.DATE, cal1.get(Calendar.DATE));
cal2.set(Calendar.HOUR_OF_DAY, cal1.get(Calendar.HOUR_OF_DAY));
//simile for whatever level of field precision is needed
Date shiftedDate = cal2.getTime();