If you want to change timestamp format like {Year, Month, Day}, then you can use this example:
I hope it will solve your problem:

timestampToDate(Milliseconds) ->
  BDate = calendar:datetime_to_gregorian_seconds({{1995,1,1},{0,0,0}}),
  Sec = BDate + (Milliseconds div 1000),
  { Date,_Time} = calendar:gregorian_seconds_to_datetime(Sec),
   Date.