Note the following problems with some records in (AB) format:
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station       yymmdd   yymmdd
  7271  CAR   851110-  851110  probably station 72712, Caribou, ME
 72327 BNA    790101-  890630  record with bad yymmdd of 832224, may be 841224
 72344 FSM    790101-  890630  record with bad yymmdd of 802205, may be 820205
 72469 DEN    790101-  890630  record with bad yymmdd of 824224, may be 830224
 91275 PJON   790101-  890701  record with bad yymmdd of 890701, may be 890630

For (AB) format hourly snow data, some stations have strange hours (see
format_snowAB)