Daylight Saving Time (DST) is a system whereby clocks are adjusted for part of the year to create more daylight in the evening hours. At the beginning of the DST period in the Spring, clocks are turned forward an hour, effectively moving an hour of daylight from the morning to the evening. When the DST period ends in the Fall, the clock is moved back one hour, returning the clock to Standard Time (ST).
DST is an issue that PI system managers must grapple with twice a year. PI 3 Servers observe DST settings, so there is very little a PI 3 system manager should need to do to prepare for DST. However, PI 2 Servers and PINet nodes do not observe DST settings; therefore, system managers must manage the DST time changes on PI 2 Servers and PINet nodes using the appropriate utility or batch file.
For all machines that are part of the PI system, it is important to be sure the time is set correctly and synchronized with the PI Server. In addition, all Windows machines should have the proper time zone settings and should be set to automatically adjust clock for Daylight Saving Time changes (see the Date and Time
control panel). If there are offsets between the nodes, there may be short time periods where data are lost, duplicated, or inserted with timestamps off by an hour. If time changes for DST are disabled, then this can result in data loss.
Click on the links below for details on issues that affect the following PI system components during DST transitions:
PI Time Stamps
PI 3 Servers store time stamps in seconds since 1970 in Coordinated Universal Time (UTC). Therefore, it is important that the time and time zone be properly set on the PI Server operating system and all interface nodes and clients in your PI system.
For most current interfaces using the extended PI API, events are sent to the server with UTC timestamps. As a result, DST and time zone differences are properly considered when storing data on the PI Server.
PI API-based clients, such as PI ProcessBook 2.x and PI Datalink 2.x and earlier, use server local timestamps.
PI SDK-based clients, such as PI ProcessBook 3.x and PI DataLink 3.x and later, utilize the UTC timestamps directly from the PI Server.
For a deeper understanding of PI time stamps consult the following:
Attention users with customized LOCALHOST.TZ files: Please see the Support Bulletin
regarding a Known Issue that can cause the localhost.tz file to be overwritten if running PI Server 3.3.362.47 to 3.4.370.58 and PI SDK 220.127.116.11 or later.