Radio Clock - Daylight Saving Time

Daylight Saving Time

Very often radio clocks have bugs in their software relating to daylight saving time (DST). This often leads to clocks not updating themselves to the correct civil local time when DST transitions on to off or off to on. Clocks that interpret longwave stations tend to be the most affected due to very minimal low level software (often hand coded assembler, or compiled C) used to decode and display the time signal.

On some systems, notably WWVB, DST is much less an issue because part of the transmitted timecode contains a "DST is now in effect" flag. Therefore even if a change in law occurs which changes the transition days (the most common change), the transmitted timecode will be updated and the clock's software only needs to pay attention to this DST flag. The only change which would typically cause DST transition problems would be if the transition time were to change (e.g. 0200 hours local time).

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