Convert date with known timezone to UTC date

Question

Date and Time Conversion has always been my weak link. I have the following values in string format:

1. String date="2015-08-21 03:15" and timezone for this date is
2. String timeZone="GMT+05:30";

Now I need to covert this date, for which I already know the timezone, to UTC date.

Answer 1

If you are given time in "GMT+05:30" timezone next code will convert it to UTC timezone:

String strDate = "2015-08-21 03:15";
String timeZone="GMT+05:30";
String format = "yyyy-MM-dd HH:mmz";
SimpleDateFormat formatter = new SimpleDateFormat(format);
Date dateStr = formatter.parse(strDate+timeZone);
formatter.setTimeZone(TimeZone.getTimeZone("UTC"));
String formattedDate = formatter.format(dateStr);
System.out.println("UTC datetime is: "+formattedDate);

Answer 2

You can try like this:

Approach 1: Using Java Date:

//Your input date string
String date="2015-08-21 03:15";

// date format your string
String format = "yyyy-MM-dd HH:mm";

//Create SimpleDateFormat instance
SimpleDateFormat sdf = new SimpleDateFormat(format);

// Convert Local Time to UTC 
sdf.setTimeZone(TimeZone.getTimeZone("UTC"));

//parse your input date string to UTC date
Date gmtTime = new Date(sdf.parse(date));

Approach 2: Using Joda time (recommended)

String dateString = "2015-08-21 03:15:00+5:30";

String pattern = "yyyy-MM-dd HH:mm:ssZ";

DateTimeFormatter dtf = DateTimeFormat.forPattern(pattern);

DateTime dateTime = dtf.parseDateTime(dateString);

System.out.println(dateTime);