An indicator of whether the admission day is on the weekend (AWEEKEND) is calculated from the admission date (ADATE). If AWEEKEND cannot be calculated (ADATE is missing or invalid), then

• AWEEKEND is missing (.) if ADATE is missing (.) or
• AWEEKEND is invalid (.A) if ADATE is invalid (.A).

Beginning in the 1998 HCUP files, the data element ADAYWK is replaced by admission weekend (AWEEKEND).