When running a SharePoint Web Service to return a date/time field of a list item, the time returned is different between the Nintex and SharePoint web services.
This is expected behavior. Nintex Web Service returns time in UTC, rather than the local time zone. To work around this, manipulate the value post web service to format to the desired time zone.
SPFieldDateTime methods in Microsoft Developer Network.
GetFieldValueAsText(Object) returns the specified field data value, expressed in Coordinated Universal Time (UTC) format, as a string. (Overrides SPField.GetFieldValueAsText(Object).) The SharePoint web service does not return the value as UTC.