Time handling

Timestamps for all data are stored in Coordinated Universal Time (UTC). The current UTC time is derived from the current local time and the time zone setting in the operating system of the computer on which the AVEVA Historian is running. During data retrieval, timestamps are returned in local time, by default. You can convert the timestamps so that they are shown in local time by using a special query parameter.

You should use the international date/time format for all timestamps used in queries. The format is:

YYYYMMDD HH:MM:SS.000

where:

• YYYY = year

• MM = month

• DD = day

• HH = hour

• MM = minutes

• SS = seconds

• 000 = milliseconds

The format for timestamps returned from queries is controlled by the default language settings of the SQL Server login. Make sure that you configure the default language setting for SQL Server logins correctly, especially in environments with mixed languages/regional settings.

If you have multiple historians and/or are using remote data sources, it is very important that you synchronize the time between the computers. For more information, see Time synchronization for data acquisition.

Make sure that you have selected the operating system setting to automatically adjust time for daylight savings, if the time zone in which the computer is located observes daylight savings time.