1. System Clock Updates

Issue

Systems or devices that include a date/time clock that adjusts ahead and back automatically for Daylight Saving Time use rules to decide when to switch from Standard Time to Daylight Saving Time. These rules need to be updated, where possible.

Recommendation

If you maintain computer devices or systems with DST-aware clocks, locate and apply any updates related to the new DST rules. This applies to personal computers, servers, handheld computing devices, phones, and embedded devices such as automatic door lock systems.

Impact

Systems that aren’t updated will have their clocks set one hour slow during the four weeks covered by the extended DST period. In addition to the clock display being wrong, it could cause confusion in cases where the time is reflected externally. Here are a few examples:

• Outgoing mail messages will be given an incorrect time stamp and incoming messages may have their time stamps incorrectly interpreted.

• Systems using older versions of Kerberos authentication may have problems if users have manually adjusted their system clock to compensate for the incorrect DST rules. UTC time stamps are involved in the original versions of the protocol, requiring clocks to be synchronized to within a few minutes.

• Processes that run at a preset time, such as unlocking a door or sending a data file to another computer for processing, may happen an hour later than expected.