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.

andy

This Plugin allows you to display time and date from all timezones. The setup page generates the shortcode you like. Just copy & paste this code on every place you want. The time is adjusted to the server time. 
Formats: 
 * Time (without seconds) 
 * Time 
 * Date (local format) 
 * Date 
 * Daten and Time

Saan World Clock

This Plugin display date and time of all timezones (Server time adjusted). Easy to use with shortcodes.

WP Server Date Time vs Saan World Clock