Sorry, I couldn't find pricing data for that day. The closing price for Microsoft (MSFT) on August 21, 2015 was $37.49. It was down 4.9% for the day. The latest price is $511.23.
DATE
OPEN
HIGH
LOW
CLOSE
VOLUME
August 21 2015
$39.43
$39.58
$37.49
$37.49
70,053,100
Daily pricing data for Microsoft dates back to 3/13/1986, and may be incomplete.