Ar hyn o bryd, yr awdurdodau lleol sy’n pennu dyddiadau tymhorau ar gyfer ysgolion cymunedol, ysgolion arbennig cymunedol, ysgolion gwirfoddol a reolir ac ysgolion meithrin, tra mai’r cyrff llywodraethu sy’n gwneud hynny yn achos ysgolion gwirfoddol a gynorthwyir ac ysgolion sefydledig. Nid oes cyfrifoldeb cyfreithiol ar y naill na’r llall i gydweithio er mwyn cysoni dyddiadau tymhorau ledled Cymru. Hefyd, aflwyddiannus hyd yma fu’r ymdrechion gan Gymdeithas Llywodraeth Leol Cymru i gysoni’r dyddiadau tymhorau hynny a bennir gan awdurdodau lleol.
Currently, local authorities set term dates for community, community special, voluntary controlled and nursery schools, while governing bodies do the same for voluntary aided and foundation schools. There is no legal responsibility placed on either of these groups to work together to harmonise term dates across Wales, and efforts by the Welsh Local Government Association to achieve harmonisation at least between term dates set by local authorities have not so far been successful.