ACR QUESTIONED ATC'S PREPARATION OF ATIS INFO LISTING EXAMPLES OF CODE AND INFO CHANGES BUT AN UNCHANGING ATIS TIME STAMP.

Narrative

THIS IS A GA SAFETY PROB/QUESTION CONCERNING ATIS RPTS. I WAS AT (CITY) AND COPIED ATIS; XA45Z; AT APPROX XB00Z. RWY 23L WAS NOTAMED CLOSED. DURING DEICING OFF THE GATE; I NOTICED THAT RWY 23L WAS BEING USED FOR DEPS AND HEARD GND CTL TELL SOMEONE THAT NEW ATIS WAS CURRENT SO I LISTENED TO NEW ATIS. THE TIME STAMP WAS THE SAME (XA45Z) AND ALL WX INFO WAS THE SAME. THE ONLY DIFFERENCE WAS THAT RWY 23L WAS NOT NOTAMED CLOSED. MY QUESTION/PROB IS; HOW CAN AN ATIS HAVE THE SAME TIME STAMP BUT A DIFFERENT IDENT AND DIFFERENT INFO? WHEN I LISTEN TO AN XA54Z ATIS ON THE HR; I ASSUME I HAVE THE MOST CURRENT ATIS WHEN I CALL FOR TAXI UP UNTIL XB50 OF THAT HR. A SIMILAR SITUATION OCCURS ABOUT ONCE A MONTH. I GET THE XA54Z ATIS; CALL FOR TAXI; AND HAVE GND CTL TELL ME THAT THE ATIS I CALLED WITH IS NOT CURRENT. SO I GO BACK AND LISTEN TO THE 'NEW' ATIS; ONLY TO FIND OUT IT HAS THE SAME TIME STAMP AND THE SAME INFO; JUST A NEW IDENT. THIS DEFINITELY CREATES AN UNNECESSARY WORKLOAD; AND HAS THE POTENTIAL TO CREATE CONFUSION AND/OR DISTR DURING ENG START AND TAXI OUT. WHOMEVER PREPARES THE NEW ATIS SHOULD ENSURE THAT A NEW IDENT IS ISSUED WITH IT. IF ANY INFO CHANGES; A NEW TIME STAMP AND IDENT SHOULD BE ISSUED.