Check for date of validity
D/S = duration of status, but if you changed from F1 to H1 then the most recent I-94 will have the date of validity. Read the card carefully it might say retain this portion for records and the other half needs to be turned in when you leave US. Earlier at the airports you could just hand in whatever I-94 came up in your dont know the current practices, i.e. if they check dates or not.