Once again the old calendar on the wall says it’s time to change the clock, trading an hour’s sleep for more evening sunshine. Most Americans will set their clocks forward one hour this weekend. Officially the change to daylight-saving time occurs at 2 a.m. Sunday, local time, though most folks will reset their clocks and watches before going to bed. The shift also serves as a reminder to install new batteries in warning devices such as smoke detectors and hazard warning radios. In areas that observe the change, standard time will return on Nov. 1.