Using Date/Time Keywords

You can use Date/Time keywords in Date/Time fields that appear on Submit, Transition, and Update forms, Change History, Deleted Items, and Trend report forms, in the Advanced Lookup Tool, and in the Relational Field Value Lookup. You can also use Date/Time keywords for report specifications and for performing calculations for Listing, Multi-Table, and Version Control Actions reports.

Note: You cannot use Date/Time keywords for values in Date/Time fields that are set to display elapsed time or as a stopwatch. For Time Only fields, now is the only available keyword. These settings are made by your administrator.
When you use Date/Time Keywords in calculation fields in Listing reports, certain calculations are not possible. For example, you cannot multiply, divide or add Date/Time Keywords. Invalid calculations will result in an error when you run the report. The error starts with:
An error occurred while processing the last request.

The error was:

Database exception in ....