dhruwal

This plugin is useful when you want to know what date time & timezone is it on server where wordpress is hosted if you are in other timezone. 
Output looks like:
Server Date/Time: Sat 06th Dec,2008 11:17 am 
Server Timezone: America/Phoenix, (MST -07:00)
Version Change log:
v0.5 
Supports upto WordPress 3.7.1
v0.4 
Supports upto WordPress 3.6
v0.3 
Minimize css code 
Supports upto WordPress 3.5.1
v0.2 
Added description before date time 
Added timezone information 
Changed text color from red to green
v0.1 
Initial release

WP Server Date Time

This plugin shows the server local current date time & timezone in the upper right of your admin screen on every page.

khill07

WordPress displays all dates and times based on a site-level timezone setting configured in the admin back-end. The problem is when you user base handles people from all over the world date and times really don’t mean much any more.
This plugin enables the user to select their own timezone and it handles the date and time conversion in both the front-end and admin section of the site.
The plan is to start out simple and improve from there. Currently, due to some complexities with time conversions, this plugin requires your site-level timezone to be set to UTC+0, UTC or some other timezone with no UTC offset. You can find this setting in the admin section under Settings -> General.
Also, please note that if you are changing your site-level timezone, this will not update any data in the database. WordPress simply assumes all date and times entered, where entered in UTC. This will unfortunately shifted all date and times by the number of hours your old timezone was offset from UTC. But please keep in mind that storing date/times in UTC is a good habit and all new date and times entered correct with not shift.

WP User Level Timezone

its work for me

Allows the site-level timezone to be changed at the user profile level

WP Server Date Time vs WP User Level Timezone