Setting the internal clock in a Cisco router allows timestamping of logging information which makes troubleshooting much easier. If you do not have an NTP server running, you can set the time manually with a simple command.
To set the time, use this command in enable mode (not configuration mode):
Router# clock set 22:55:05 June 19 2006
The time is in 24-hour mode. To see the information about the clock settings, use the following:
Router# show clock detail
22:56:07.136 PDT Mon Jun 19 2006
Time source is user configuration
This will show the current date and time and the source of the time configuration (in this case showing that the time was manually set).