St David's Day: Why is it celebrated on 1 March?
1 March 2013 Last updated at 08:21 GMT
A survey published by the historic monuments body Cadw suggests that half of adults in Wales do not know why the country celebrates St David's Day on 1 March.
It is thought that that was the day he died, in 589 AD.
Gareth Lewis went to meet a class of schoolchildren who have been doing their homework on Wales' patron saint.