Worldwide celebrations for St Patrick's Day could face disruption after the Catholic Church decided to move the Irish patron saint's feast day.
Bishops were left with sore heads after they discovered the traditional March 17th festivities will clash next year with the second day of Holy Week.
Under the Church's rules, the General Norms for the Liturgical Year and Calendar, the saint's feast day does not rank as high as the Monday before Easter and has to be moved.
After much deliberation, Rome gave Irish authorities the green light to shift the official religious celebrations two days back to March 15th, which falls on a Saturday.
Fr Peter Jones, of the Liturgy Commission, insisted the move was necessary under the laws that govern the Church diary.
"It's about the religious aspect of the feast and mass on the day. It's not about whether it's a public holiday or not, it's not about whether sports events and parades take place," he said.
"It's about the Holy Day which can't be observed on the Monday of Holy Week and therefore has to be transferred in accordance with the usual rules."
In strict accordance with the rules, next year's St Patrick's Day should have been moved to the next available day in the Church's calendar, which is April 1st.
But senior Irish clerics were anxious to keep the date as close as possible to the international civic celebrations, which are often planned many years in advance.
The Vatican approved the irregular step of moving the day backwards next year to January 20th, but details have only just emerged.
The last time St Patrick's Day had to be moved was in 1940 when it was changed to April 3 rdbecause it coincided with Palm Sunday, the first day of Holy Week.