Handling time zone in web application

Question

In our web application we need to show and enter date time information for different countries in different time zone. Right now, we are maintaining separate web server and

Answer 1

I would simply transform the existing dates stored in the DB into Long, and persist (ETL process) this Long value, along with the known (or deducted) pattern, Locale and TimeZone (default meta). And persist any new Date as long as with the default meta.

ETL example

Let say 2015-11-29 10:07:49.500 UTC is stored in the DB:

// Known or deducted format of the persisted date
String   pattern = "yyyy-MM-dd HH:mm:ss.SSS"; 
Locale   locale  = Locale.ENGLISH;
TimeZone zone    = "UTC";

// Date to ms
SimpleDateFormat sdf = new SimpleDateFormat(pattern, locale);
sdf.setTimeZone(TimeZone.getTimeZone(zone));
Date date = sdf.parse(pattern);

// ETL: Can now be persisted in Long, along with default META (pattern, Locale, TZ)
Long dateL = date.getTime(); // for e.g. 1448827660720
...

The persisted Long value can also be transformed in any other format, if needed

pattern                  | locale   | tz   |  result
============================================
yyyy/MM/dd               | null     | null |  2015/11/29          
dd-M-yyyy hh:mm:ss       | null     | null |  29-11-2015 10:07:40
dd MMMM yyyy zzzz        | ENGLISH  | null |  29 November 2015 Central European Time
yyyy-MM-dd HH:mm:ss.SSS  | null     | UTC  |  2015-11-29 10:07:49 UTC