I am using PIArcVal() to retrieve previous values to a given time stamp. I have been using this for a few years now but suddenly this week my unchanged Excel2007 workbook has started behaving oddly.

A formula, =PIArcVal(tag, "05-Jan-11 00:00:00", 1, PIServer, "previous") works and provides data like this:
04-Jan-11 23:58:00
04-Jan-11 23:30:01
04-Jan-11 23:37:59

However if I place the date in a cell and refer to it thus =PIArcVal(tag, B$1, 1, PIServer, "previous")I get this data returned:
30-Apr-11 23:58:00
30-Apr-11 23:30:01
30-Apr-11 23:37:59


Looking at the actual numbers in the time stamp, 05-Jan-11 = 40548. However PI is treating this not as 5/1/2011(5th Jan) but as 1/5/2011(1st May). The day prior to 1st May is of course the 30th Apr hence the values returned.

The timestamp is formatted as dd-mmm-yy and the PI Settings also uses that same format.

Has anyone else seen this behaviour or have any idea how to solve?

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After much head scratching (and me using other PC's!) we finally decided to wipe the hard disc and start a fresh. Glad to say that this DID work.

Case closed.

hi squatty,

never even thought to try reinstalling just Office. but then it was probably just easier to rebuild the PC OS from a ghost image anyway.

Miles