A Daylight Saving Time patch is a modular piece of code created to update systems, devices and programs for compatibility with new start and end dates for Daylight Saving Time ( DST ) in the United States, Canada and Bermuda.
The changes to Daylight Saving Time, mandated in the U.S. Energy Policy Act of 2005, extend DST three weeks in the spring and one week in the fall. Starting March 11, 2007 clocks spring ahead an hour on the second Sunday in March and fall back on the first Sunday in November. The assumption behind the change was that it would decrease the need for artificial light sources and, as a result, save energy.
Time discrepancies could cause scheduling and synchronization problems for unpatched operating systems, applications and devices. Indirectly, the changes may affect not only systems in these areas but also systems that interact with them.