Summary: St Laserian This image (<left) shows a carving on a pulpit in the Cathedral of the Assumption, Carlow: it shows St Laserian addressing the Synod of Leighlin in 630 AD where he defended the Roman method of calculating Easter. He is the patron saint of Leighlin diocese.
Patrick Duffy tries to sort out what is known about him.
Associated with Old Leighlin in Co Carlow
There are at least four saints of this name, Laserian :
one is associated with Devenish Island in Co Fermanagh;
another is associated with Inishmurray, Co Sligo;
another was the third abbot of Iona.
The one of this feast day is associated with Old Leighlin in Co Carlow and is the patron saint of Leighlin diocese.
A Disciple of St Munnu 
Laserian was the son of Cairel de Blitha and Gemma, a Scottish princess and may have spent his early years in Scotland. He was also said to have been a disciple of St Munnu (Fintan of Taghmon? See 21st October).
Roman Education
He is said then to have spent fourteen years in Rome and studied under St Gregory the Great, who ordained him and sent him back to Ireland (?). At any rate he was a strong proponent of the Roman method of calculating Easter. When he came back to Ireland, he took over an already established monastery from St Gobban at Leighlin (Leth-glen, half-glen, a fold in the hills), Co Carlow. Leighlin then became a strong centre of support of the Roman method of calculation.
Contest of Miracles with St Munnu
However, his former teacher Munnu at the Council of Maigh Ailbe on the borders of Kildare and Carlow challenged Laserian to a contest of miracles. He suggested they would throw the books containing the old and new calculations of Easter in the fire to see which burned. Laserian declined this as unfair, saying: “If you Fintan told Slieve Margy over there to move to Magh Ailbe, and Magh Ailbe over to where Slieve Margy is, God would do it for you.” It took some decades for the Roman way of computing Easter was finally accepted and approved at the Synod of Whitby (664).
Association with Maighnean of Kilmainham
Another story about Laserian is told in the Life of Maighnean of Kilmainham. Maighnean found Laserian lying crossways in a hovel suffering from thirty diseases. “My sinfulness goes like a flame through my body, for I want to have my purgatory in this life and find eternal life in the next. For the grain of wheat must be threshed and beaten before it is sown in the earth. So it is with me before I am laid in the grave. I want my body threshed with infirmities.” In the end Laserian asked Maighnean to preside at his funeral.
St Laserian’s Cathedral in Old Leighlin
The present Cathedral in Old Leighlin was begun by Bishop Donatus of Leighlin (1152-81) and completed by the end of the 13th century. One of the oldest items in the Cathedral is an 11th century font. The cathedral was taken over by the Anglican Communion (Church of Ireland) at the time of the Reformation. A new Roman Catholic Cathedral (Cathedral of the Assumption) designed by Thomas Cobden was completed in Carlow town in 1833.
