Java SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'") gives timezone as IST

You haven't set the timezone only added a Z to the end of the date/time, so it will look like a GMT date/time but this doesn't change the value.

Set the timezone to GMT and it will be correct.

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'");
sdf.setTimeZone(TimeZone.getTimeZone("GMT"));

'T' and 'Z' are considered here as constants. You need to pass Z without the quotes. Moreover you need to specify the timezone in the input string.

Example : 2013-09-29T18:46:19-0700 And the format as "yyyy-MM-dd'T'HH:mm:ssZ"

From ISO 8601 String to Java Date Object

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'");
sdf.setTimeZone(TimeZone.getTimeZone("GMT"));
sdf.parse("2013-09-29T18:46:19Z"); //prints-> Mon Sep 30 02:46:19 CST 2013

if you don't set TimeZone.getTimeZone("GMT") then it will output Sun Sep 29 18:46:19 CST 2013

From Java Date Object to ISO 8601 String

And to convert Dateobject to ISO 8601 Standard (yyyy-MM-dd'T'HH:mm:ss'Z') use following code

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.US);
sdf.setTimeZone(TimeZone.getTimeZone("GMT"));           
System.out.println(sdf.format(new Date())); //-prints-> 2015-01-22T03:23:26Z

Also note that without ' ' at Z yyyy-MM-dd'T'HH:mm:ssZ prints 2015-01-22T03:41:02+0000