About VTScada and Time

VTScada records events using UTC (Coordinated Universal Time). All alarms, logged data, operational events, and everything else that has a time stamp, is recorded using UTC. This ensures that records are stored correctly, even if you have servers in multiple time zones. Time is stored using UTC.

VTScada displays time using your local time zone. This applies to reports, the Historical Data Viewer (HDV), and the clock at the top of each page. It applies whether you are at a workstation with VTScada installed, or are using a thin client connection to view a server in another time zone. Time is displayed using your time zone.

Accuracy of time depends on your computer being configured for the correct time and time zone. If you are in New York, but have configured your operating system to think that it is in London, England, then events will be recorded in UTC using an offset calculated for London, not New York. VTScada will also display times for London, not New York. It is important that you configure your servers to have the correct time and time zone, wherever they are located.

If you manually change the time or the time zone on your computer, you must restart VTScada. Failure to do so can result in inaccurate recording of timestamps.

A very limited number of VTScada's user interface tools can be configured to display time using either the time zone in effect at the server where an event is generated, or the local time. For example, Roster tags can be configured to use either the contact's stated time zone or the time zone of the current Alarm Notification Server. These tools are exceptions. For most of the user-interface, the rule stated above applies: time is displayed using the local time zone.

Viewing Trends and Reports after a Daylight Savings Time Shift

Both the HDV and the various reports display the data from a requested period of time using the start time you specify and an offset from that start time. (If a report configuration uses both a start time and an end time, the offset is calculated by subtracting the first from the second, before querying the history.) You will see all the records that exist from the start time through the length of the offset time. Attempting to view a full day's data (24 hours) on a trend at midnight after the shift to Daylight Savings time (a 23-hour day) can result in an hour-long flat line at the end of the trend.