CODEWITHSUNDEEP
javajqueryjsptimezonedatatables
Chris Quibell
Chris Quibell

Reputation: 339

Java-Adding timezone to date when date is grabbed from datepicker

I have a jsp page that takes the value from a jquery datapicker and passes it into a search. The user of the site has the opportunity to change their timezone to fit where they are located in the world. I want to take the value searched which is based off the browsers time and format it and show it on screen with the user’s timezone.

The column is expireDate and I use datatables to display the results. 

{
    "mData":"expireDate",
    "mRender":function(source,type,full){
    if(-1==source)
    return "";
    var toDate = new Date(source);
    var stringDate = toDate.toString(dateTableFormater);
    return stringDate;

I get the value and pass in my own custom formatting, the formatting is based on where the person lives. Each format is different depending on where they live and prevents me from using the simpledateFormat.setTimezoneOffset();

$("#expireFrom").datepicker($.datepicker.regional[plannerLang]);
    $("#expireFrom").datepicker( "option", "dateFormat",dateFormater);
    $("#expireTo").datepicker($.datepicker.regional[plannerLang]);
    $("#expireTo").datepicker( "option", "dateFormat",dateFormater);

I have a dto set up so it gets the users Timezone, I just cant figure out how to implemet that so when the time is sent back to the jsp the timezone has been included in the time. How do you add/subtract the timezone difference from the date that the browser has gotten?

Upvotes: 0

Views: 1062

Answers (1)

Basil Bourque
Basil Bourque

Reputation: 338875

Adjust for Time Zone Offset

Computers track time in a universal manner, free of time zone information. They use a count of seconds/milliseconds/nanoseconds since an epoch. So adjusting for time zone is not a matter of adding or subtracting to the time itself. It's a matter of adjusting the expression of that time/count as a string.

Joda-Time

The bundled java.util.Date/Calendar classes are notoriously bad in both design and implementation. You should use a competent date-time library instead. Currently, that means Joda-Time. In the future, with Java 8, you can continue with Joda-Time or switch to the new bundled java.time.* classes defined by JSR 310. Those classes are inspired by Joda-Time but are entirely re-architected.

A DateTime instance in Joda-Time knows its own time zone, unlike a java.util.Date.

Server Time

Most programmers find it wiser to use the server's clock rather that obtain time from the user’s machine. Users’ machines are notorious for being out of sync with the correct time. That is less true today with the Internet and NTP servers. Nevertheless, I suggest you stick with server’s clock.

From the user’s machine you should obtain their Locale information, country (culture) and language.

By the way, usually best to work in UTC (no time zone offset) in your business logic and switch to a time zone only for presentation to user.

Example Code For Time Zone

// © 2013 Basil Bourque. This source code may be used freely forever by anyone taking full responsibility for doing so.
// import org.joda.time.*;
// import org.joda.time.format.*;

DateTimeZone timeZone = DateTimeZone.forID( "Europe/Athens" );

DateTime now_Athens = new DateTime( timeZone );
DateTime now_Seattle = now_Athens.toDateTime( DateTimeZone.forID( "America/Los_Angeles" ));
DateTime now_UTC = now_Athens.toDateTime( DateTimeZone.UTC );

Dump to console…

System.out.println( "now_Athens: " + now_Athens );
System.out.println( "now_Seattle: " + now_Seattle );
System.out.println( "now_UTC: " + now_UTC );

When run…

now_Athens: 2014-01-02T20:11:43.657+02:00
now_Seattle: 2014-01-02T10:11:43.657-08:00
now_UTC: 2014-01-02T18:11:43.657Z

Formatting Strings

Joda-Time has many features for rendering strings via formatting:

  • You can format with Locale-sensitive Long, Medium, Short formatters.
  • You can define your own formats.
  • You can go with standard ISO 8601 formats, the default, as seen above.

Example Code For Formatting

DateTimeZone timeZone_Paris = DateTimeZone.forID( "Europe/Paris" );
String nowLocalizedParis = DateTimeFormat.forStyle("LS").withLocale(Locale.FRANCE).withZone( timeZone_Paris ).print( now_UTC );

Dump to console…

System.out.println( "nowLocalizedParis: " + nowLocalizedParis );

When run…

nowLocalizedParis: 2 janvier 2014 19:11

Upvotes: 3

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