title: Mobile app and server
body: <p>Im writing an android app and need to get data from a server.
  How can I know if there changes in the data whithout downloading all data every time ?</p>
  
  <p>Do you think relying on date and time will work? I mean:
  if the server tells apps last time updated was at 11.00
  and current time is 11.01 this means there are updates { servers also tells me specifically what updates have been made
  }
  else no updates</p>