Mae awdurdodau lleol a chyrff llywodraethu ysgolion gwirfoddol a gynorthwyir ac ysgolion sefydledig yn cadw'r hawl i bennu dyddiadau tymhorau ar gyfer eu hysgolion. Fodd bynnag, mae ganddynt ddyletswydd i gydweithredu a chydlynu â'i gilydd er mwyn sicrhau bod dyddiadau tymhorau’r un fath, neu mor debyg â phosibl (adran 32A o Ddeddf Addysg 2002).
Local authorities and the governing bodies of voluntary aided (VA) and foundation schools retain the right to set term dates for their schools. However, they are under a duty to co-operate and co-ordinate with each other to ensure that term dates are the same or as similar as possible (section 32A of the Education Act 2002).