From Garmin's Website:
Q. My GPS clock is one hour off after the Daylight Savings (DST) change. How do I fix this?
A. In accordance with the Energy Policy Act of 2005, in 2007 Daylight Savings for the United States starts Sunday, March 11th. In order to reflect this change in our GPS units, software updates will be released to accommodate the change. As of March 8th, updates have been released for the StreetPilots 2720, 2730, 2820, 7200, 7500, c310, c320, c330, c510, c530, c550, i2, i3, i5, BMW Navigator III, and nüvi 360. To update those devices, please use our WebUpdater software update program. Updates for other units will be released as they are available. Periodically running WebUpdater with your GPS unit connected to the computer will check for updates.
If an update is not available for your unit to reflect the change to the new start of Daylight Savings Time, please refer to the owner's manual to manually change the time.
The discontinued units are still waiting for an update for the DST changes. You can access the Time functions from the 'Systems Settings' menu and set the DST setting to 'On' manually.
Here's the location for the 2610 manual if you need it.