One of my current projects involves developing an internal system to keep track of the technologies that are approved for use in our solutions.  As part of that, I’d like to set a flag on each entry so that it is regularly reviewed – for example every 90, or 180 days.

I had hoped to use a calculated column for this (i.e. today’s date plus x days) but it’s generally recognised that calculated fields only work on data entered by a user, and not from the system. Indeed, Microsoft’s own documentation for the TODAY function says:

“[…] You can use the TODAY function only as a default value; you cannot use it in a calculated column.”

Even so, I’ve had some success (with Microsoft Office SharePoint Server 2007) in setting a column type of Date and Time, in Date Only format, with a Calculated Value of =Today+90.  I’m not sure how/why this is working, given Microsoft’s statement above, but it may be worth considering.  Just be aware that your mileage may vary…

(Christophe Humbert has more information and another approach over at Path to SharePoint)