Returned in the /Logon URL’s GET response and must be included in all URL request headers.

Returned in the header of all responses that return data. If the client is going to cache, the data should use this file as the file-time (in conjunction with the If-Modified-Since header variable).

Included in any GET request that returns data, except requests for Sample or Quota data. The MobileSyncWebService compares the If-Modified-Since time, in the incoming request, to the requested data's last modified time. The variable returns a 304 status response when the times are identical.

The header must be included to enforce the returned XML format.