On some cisco devices when you are connected to the console or view the logfile (show logging) you get an output with the uptime of your device.
1y35w: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/4, changed state to up
This switch has been up for 1 year and 35 weeks.
Your config propably set like:
service timestamps debug uptime service timestamps log uptime
If you want to set your logging to timestamp you can change that with the Service timestamps command. This has to be set for debug and logging seperatly.
To configure your device for timestamp debugging type:
config t service timestamps debug datetime localtime
To configure your device for timestamp logging type:
config t service timestamps log datetime localtime
All the new entries in your logging will show the timestamp in front!
Don’t forget to set the clock of your device!