You can perform arithmetic operations on numeric date fields in the same manner as on any numeric data item. Where appropriate, the century window will be used in the calculation.
. However, there are some restrictions on where date fields can be used in arithmetic expressions and statements. Arithmetic operations that include date fields are restricted to:
The following arithmetic operations are not allowed:
Date semantics are provided for the year parts of date fields but not for the nonyear parts. For example, adding 1 to a windowed Gregorian date field that contains the value 980831 gives a result of 980832, not 980901.
related tasks
Allowing for overflow from windowed date fields
Specifying the order of evaluation