You may be celebrating St Patrick's Day today as normal, but, at least according to Catholics and Anglicans, you're making a slight mistake. Why is that?
St Patrick's Day is on 17 March every year. It's an opportunity for Christians around the world to recognise the life of the patron saint of Ireland.
But the feast day is also characterised by parades and boisterous revelry. Traditionally a major event in Ireland, the festival has spread around the world with the movement of Irish immigrants and is now even celebrated in locations like Moscow and Tokyo, which have no significant Irish populations.
This year the extremely early arrival of Easter has forced changes to St Patrick's Day.
The Catholic Church in England and Wales says St Patrick's Day is simply not on the calendar of feast days this year. This week is known as Holy Week in the church and takes precedence over all saint's days.
Any saint's feast day that clashes with it is omitted from the calendar.
But the position is different in the Republic of Ireland, where St Patrick's Day was observed on Saturday 15 March, instead of Monday 17 March.
Holy Week
Rev Martin Long, a spokesman for the Irish Bishops, said it was a "very, very unusual" step but due to the early Easter, the Church was celebrating the feast on Saturday, two days early.
"The reason the solemnity of St Patrick was moved from 17th to the 15th is because it happens to fall this year in Holy Week," he says.
"And the liturgy of Holy Week ranks above all others so St Patrick had to be moved to another date. The Catholic Church of Ireland purposefully decided to celebrate it on the 15th so it was as close as possible to the civic celebration, which is on the 17th."
For the Church of England, St Patrick's day is celebrated as a "lesser festival" and where that falls between Palm Sunday and Easter Sunday it is normally omitted. But the church's rules allow individual ministers to stage a celebration on the next available day, where "there is sufficient reason".