Result is the datetime obtained by adding a duration (second argument) to a datetime (first argument).
Durations must be entered in the form: P1Y2M3DT04H05M. Periods can be made negative by adding the minus character before the P designator, e.g. -P1D.
P is the period designator, and is mandatory; the rest of above period is therefore:
1 Year, 2 Months, 3 Days T(ime designator), 04 Hours, 05 Minutes.
The example shown below, adds 10 days to the departuredatetime, i.e. P10D.
E.g. Instance document datetime:
To extract yesterdays date from dateTime input, use the "now" function to input the current date/time including timezone. A period can be made negative by using the minus character before the P designator, e.g. -P1D (minus 1 day).
E.g. datetime now is 28th Feb 2012, 17:19:54.748(millisec)+01timezone.
i.e. 27th Feb 2012, 17:19:54.748(millisec)+01timezone