I am doing a server for updating a pass in passbook. I can register and unregister it from server. Next, I have to get serial of pass and latest version of pass when a pass is updated. what is differences between If-Modified-Since and lastUpdated ? I don't know how to get them ? are they from my database or what else ?
If-Modified-Since is a HTTP header that you send with the .pkpass bundle. If you do not initially distribute the pass by a web server, your Passbook web service should send it in response to the "Get latest version of a pass" request.
lastUpdated is a tag that you store in your database that indicates when the .pkpass bundle was last changed.
Both of these should match the same point in time. Convention is to send the If-Modified-Since header as a RFC 1123 formatted date and to store the lastUpdated tag as a timestamp, although it fould be perfectly acceptable to also store it as a formatted date.