  "the traditional seasonal festivals in Wales were Calan Gaeaf (Hallowe'en), Calan Mai, and Midsummer.
Additionally, each parish celebrated a Gwyl Mabsant in commemoration of its native saint. " wikipedia "The patronal festival (Gwyl Mabsant) was the day in times gone by when Welsh people celebrated their local saint. On that day they celebrated by going to church and then enjoyed themselves playing games, dancing and singing and drinking. The day was a chance to remember and enjoy themselves, their religion was full of joy. But then, as the Welsh turned to nonconformity, things like games, singing and dancing became taboo.
Over time, many of the old customs were lost as the religion of the Welsh became more serious and sober. Today, everybody remembers and celebrates March the first as St David's day - Wales' patron saint. But how many remember those other early saints whose names are recorded in the names of churches and places throughout the country? Look at a map of Wales. How many place-names being in "Llan" - a piece of land with a wall around it where the earliest churches were built. Many have the names of a Celtic saint such as Dewi (David), Teilo or Padarn - saints of the fifth and sixth centuries usually.
Others have the names of Mair (The Virgin Mary), Mihangel (St Michael) and Pedr (St Peter) - churches which belong to the 12th century onwards. " acen.co.uk 
