On a Blackberry you can have the Blackberry check servers for the correct time or you can manually set the time. Most people prefer the Blackberry keep the time correct using the time servers.
To choose the method to set the time go to the Options in menu and choose Date/Time. Then go to Date/Time Source and choose it. Then you can choose to use Network, Blackberry or Off. Choosing network keeps it updated off the wireless tower you are currently connected to. Choosing Blackberry has it update off the Blackberry servers which should be getting time off time servers. Choosing off means the time is never updated back with the time servers.
If you choose off and the Blackberry does not keep time accurately you will need to go to Date/Time to set it. Click on the Time entry and you can change the time. You can also choose your time zone. It will automatically know just as your PC when to start and end daylight savings.
Changing the time in Windows just involves clicking on the time on the bottom right of the screen and then choosing to Change Date and Time and changing it. You can choose to have it automatically synchronize with Internet time severs.
Thanks Bobby for the question.