Rockwell Automation FactoryTalk Historian SE DataLink 4.2 User Guide - Manual (Page 95)

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PI Times can also be expressed using certain constants:
Constant Result
* The current time.
Today or t 12:00 am of the current day.
Yesterday or y 12:00 am of the previous day.
Sunday or sun 00:00:00 (midnight) on the most recent past Sunday (in reference to the
Historian Server).
FactoryTalk Historian Time Expressions
FactoryTalk Historian allows three types of time expressions: relative time,
combined time, and absolute time. These time expression types are defined
in the following table.
Expression Description Examples
Relative Time Relative time expressions specify a number of days, hours,
minutes, or seconds with either a leading plus sign or a
leading minus sign.
The reference time, or starting time, for the relative time
expression is the current time if both start and end times are
relative.
+1d
-24h
-3m
+24s
Combined
Time A combined time expression is a specific reference time
followed by a relative time expression. *+8h
18-dec-02 -
3m
t+32s
Absolute Time An absolute time expression is any time expression that is
neither a relative nor a combined time expression.
*
14-Dec-97
11-Nov-96
2:00:00.0001
t
y