Changes have been made to the DateTime type in v2.0 to help indicate whether a specific value represents a local time or universal time. What this can mean is that the behaviour of web services using DateTimes will change. This article has full details of the issue:-
http://blogs.msdn.com/mattavis/archive/2005/10/11/479782.aspx
The same approach is available under .NETCF v2.0 to request the old v1 behaviour - add a configuration file for your exe with the following content:-
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<system.xml.serialization>
<dateTimeSerialization mode="Local" />
</system.xml.serialization>
</configuration>