However, the national lockdown between December 2020 and March 2021 due to the coronavirus (COVID-19) pandemic meant that the census date was delayed to 20 April 2021.
Fodd bynnag, oherwydd tarfu’r pandemig, cafodd llawer o gystadlaethau eu gohirio; fel y cyfryw, mae angen bod yn ofalus wrth ddod i unrhyw gasgliadau ar sail data 2020 i 2021.