What president was the first to declare thanksgiving a national holiday to be held on the 4th Thursday in November?

In 1941, Congress passed a bill, and Franklin D. Roosevelt signed it, that fixed the date of Thanksgiving as the fourth Thursday in November. FDR attempted to move the holiday to the third Thursday in November, but Congress enacted a law to fix the date at the fourth Thursday in November, thus making it an "official" holiday. On November 26, 1941, FDR signed the bill.