Hi there. My name is*****'m sorry that you're having this problem. I'll do my best to help.
By default, each time that you turn on your device, it should connect to satellites and automatically detect the time zone and current time of day. Please go outdoors to an open area and orient the front of the device to the sky. Wait 30 to 60 seconds for the device to acquire satellite signals.
If that doesn't update the clock, the time can be manually set by adjusting the clock settings. Select SETTINGS>SYSTEM, then go to CLOCK>SET AUTOMATICALLY>OFF. Select SET TIME and enter the time of day.
You may want to consider a factory reset rather than changing it to manual. Here's how to do that.
1.Power off watch (press and hold Light, Yes on prompt)†2.Press and hold Start/Stop and Lap/Reset3.Press and hold Light (three buttons should now be pressed in)4.After first beep, release Start/Stop5.After second beep, release Lap/Reset6.Release Light
Please give this a try and let me know how it works for you. If this solves the problem, would you mind taking a moment to rate my service? You can give your rating by selecting the stars located on the top right of the question page. I'd really appreciate it! Without a positive rating I am not credited for my answer. If this doesn't solve the problem be sure to let me know so we can continue troubleshooting.
Here's a link to the user manual for your particular Garmin for future reference.
This manual is in pdf format and can be saved to your computer for later viewing or printed out (just keep in mind that it is 24 pages).