Daylight Savings Time on ProCurve Switches

Before configuring a “User defined” Daylight Time Rule, it is important to understand how the switch treats the entries. The switch knows which dates are Sundays, and uses an algorithm to determine on which date to change the system clock, given the configured “Beginning day” and “Ending day”:

■If the configured day is a Sunday, the time changes at 2am on that day.

■If the configured day is not a Sunday, the time changes at 2am on the first Sunday after the configured day.

This is true for both the “Beginning day” and the “Ending day”.

With that algorithm, one should use the value “1” to represent “first Sunday of the month”, and a value equal to “number of days in the month minus 6" to represent “last Sunday of the month”. This allows a single configuration for every year, no matter what date is the appropriate Sunday to change the clock.

E-3