转换GMT日期为IST

Question

I am trying to convert GMT time to IST using the following piece of code:

 SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
 Date date1 = sdf.parse("2015-01-25");
 sdf.setTimeZone(TimeZone.getTimeZone("IST"));
 Log.d("date",sdf.format(date1));

However, 2015-01-24 is being logged out in console.Where am i wrong?

Answer 1

Since you are on IST, you have to manually specify GMT. Like this,

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
sdf.setTimeZone(TimeZone.getTimeZone("GMT"));  // set this if your timezone is different

Date date1 = sdf.parse("2015-01-25"); // now time is Sun Jan 25 00:00:00 GMT 2015
sdf.setTimeZone(TimeZone.getTimeZone("IST"));
Log.d("date",sdf.format(date1)); // now time is Sun Jan 25 05:30:00 IST 2015

Since IST = GMT + 05.30, you will get the same date.

Answer 2

The code snippet converts 2015-01-25 00:00:00 local time (whatever that is - seems to be east of IST) to IST and prints the date part of it.

So 2015-01-26 can never be output as IST would have to be at least 24 hours ahead of local time.