Daylight savings time and electronic clocks: a confusing combination

j0232239.gifIt used to be simple. On the first day of daylight savings time I would walk around the house and reset all the clocks. Until I got around to doing that, I would simply add an hour in my mind.

These days, when I wake up on that "spring forward" Sunday morning, Iâ''m not really sure what time it is until I turn on my cell phone. I take it on faith that the cell phone system updated on schedule. Then I have to go around the house and figure out which clocks have reset themselves and which still need to be reset. This is not always predictable.

The clocks in the cars, the coffee maker, and on the walls will stay on standard time until I reset them; they make no attempt to reset themselves.

My camera and video recorder will once again display the correct time after months of being an hour off. (I never set them back in the fall, my bad.)

Last year my Apple computer, confused by the recent rescheduling of daylight savings time in the U.S. (Congress moved it three weeks earlier in 2007), did not reset automatically. This year, thanks to a software update, it should reset its clock automatically. Microsoft has also sent out daylight savings time updates for its products; as long as youâ''re updating your computer regularly, youâ''re covered.

My watch will wait until I reset it; my sonsâ'' watches are set automatically via radio signal, provided by the National Institute of Standards and Technology, so they should reset themselves. However, they may not; I recall the manual advises to put them near a window on occasion to make sure they get a strong signal. Iâ''ll have to remind the boys to check their watches, or leave them on a windowsill the night before.

A Tivo (if I had one) would get an automatic clock correction from the mother ship. The DVD/VCR units that I do have hypothetically get updates, setting their clocks automatically to a time signal sent on the local PBS channel. This doesn't always work; back in 2000, some Los Angeles clocks ended up on New York time, other clocks were off by minutes, some by hours; the problem cropped up all around the country, depending on system quirks at local PBS stations. (I reported on this problem in the October 2000 issue of IEEE Spectrum.) The DVD/VCR that I have hooked up to the rooftop antenna will likely get its update. The other unit, which we use to play only, not to record, wonâ''t. It knows about daylight savings time, only it thinks itâ''s coming three weeks from now. Since this VCR functions as my bedroom clock, I canâ''t ignore it, instead, Iâ''ll reset it, and then, three weeks from now, reset it again after it jumps forward an hour.

After, of course, I go flying out of bed in a mad rush, convinced I'm desperately late, having forgotten about automatic clocks and daylight savings time by then.

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