Milestone Basis+ 6.5 - Manual (Page 134)

Milestone XProtect Basis+ 6.5; Administrator’s Manual
Daylight Saving Time
Daylight saving time (DST, also known as summer time) is the
practice of advancing clocks in order for evenings to have more
daylight and mornings to have less.
Typically, clocks are adjusted forward one hour sometime during
the spring season and adjusted backward sometime during the fall
season, hence the saying spring forward, fall back.
Note that use of DST varies between countries/regions.
When working with a surveillance system, which is inherently
time-sensitive, it is important to know how the system handles
DST.
Clocks are adjusted forward when
DST starts
Spring: Switch from Standard Time to DST
The change from standard time to DST is not much of an issue since you jump one hour forward.
Typically, the clock jumps forward from 02:00 standard time to 03:00 DST, and the day thus has
23 hours.
In that case, there is simply no data between 02:00 and 03:00 in the morning since that hour, for
that day, did not exist.
Fall: Switch from DST to Standard Time
When you switch from DST to standard time in the fall, you jump one hour back. Typically, the
clock jumps backward from 02:00 DST to 01:00 standard time, repeating that hour, and the day
thus has 25 hours.
In that case, you will reach 01:59:59, then immediately revert back to 01:00:00. If the system did
not react, it would essentially re-record that hour, so the first instance of, for example, 01:30
would be overwritten by the second instance of 01:30.
Because of this, XProtect Basis+ will forcefully archive (see page 101) the current video in the
event that the system time changes by more than five minutes. The first instance of the 01:00
hour will not be viewable directly from access clients (Remote Client and Smart Client; see page
137). However, the data is recorded and safe, and it can be browsed using the Viewer application
(see page 135) by opening the archived database directly.
www.milestonesys.com Page 134 Daylight Saving Time