NEW YORK -- When daylight-saving time starts earlier than usual in the United States come 2007, your VCR or DVD could start recording shows an hour late. Cellphone companies could give you an extra hour of free weekend calls, and people who depend on online calendars may find themselves late for appointments.

An energy bill President Bush is to sign today would start daylight time three weeks earlier and end it a week later as an energy-saving measure.

And that has technologists worried about software and gadgets that now compensate for daylight time based on a schedule unchanged since 1987.

''It is unfortunately going to add a little bit of complexity to consumers," said Reid Sullivan, vice president of Panasonic Consumer Electronics Co. ''In some cases, depending on the product, they may have to manually increase or decrease the time."

The upcoming transition evokes memories of Y2K, the Year 2000 rollover that forced programmers to adjust software and other systems that, relying on two digits for the year, never took the 21st century into account.

''It wouldn't be a society-wide catastrophe, but there would be a problem if nothing's done about it or we try to move too quickly," said Dave Thewlis, executive director of a group that promotes standards for calendar software.

Newer VCRs and DVD recorders have built-in calendars to automatically adjust for daylight time. Users would have to override them. Computers with Windows operating systems would need to obtain updates. Though most affected applications would probably be taken care of by the Microsoft fix, calendar systems will need to be checked.

Technologists sounded louder alarms as the year 2000 approached. A programming shortcut caused some computers to wrongly interpret 2000 as 1900, potentially fouling computer systems.

Businesses and governments threw $200 billion at the problem.

© Copyright 2006 Globe Newspaper Company.