WSS 3.0 Web Services – How To Update Date/Time Values
When adding or updating list items using the WSS Web Service ‘UpdateListItems’ method you need to pass data / time values as strings. The format should be passed in the form ‘yyyy-mm-ddThh:mm:ssZ”.
This specifies a ISO date/time format with time zone information. The “Z” indicates that the time is in “Coordinated Universal Time” (UTC).
The “ToString” method for a DateTime object (e.g. “dt” below) can be used to format a date/time using this format by passing the “u” format descriptor:
String s = dt.ToString(“u”);
Note that the DateTime object must first be converted from local time to UTC. The DateTime “ToUniversalTime” method will do this.