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.

ezraverheijen

This lightweight plugin can be used if the scheduled post feature is not working for you (missed scheduled post errors), and you host your site in a European country using CEST in the summer and CET during the winter.

WP TimeZone

Takes care of publishing posts that missed their schedule, for CET/CEST time zones only.

WP Server Date Time vs WP TimeZone