Have you ever wondered how Santa gets around the world in just one night, carries all those presents and makes sure they get to the right person?
With the most magical night of the year upon us and as millions of girls and boys around the world prepare for Daidí na Nollag's arrival, RTÉ News has asked some experts to explain some of the big mysteries of Christmas Eve.
They say most of it can be explained by science the rest by a little bit of magic!
The list: how does he keep track?
Santa has been around for thousands of years. So for a long time paper and pen were his staple tools.
However, it took a LOT of paper. Santa Claus is also known to be a trailblazer when it comes to the use of technology.
These days the elves input the information they receive in all the letters into a giant digital database and in recent years Santa has been using Artificial Intelligence to help cut out the huge amount of manual work that used to be involved in making his list and checking it twice.
Artificial Intelligence Ireland Mark Kelly explains: "Santa is really ahead of the game because Santa has been able to scan all the different letters using artificial intelligence to ensure that every child gets the present they want."
The presents: how does he carry them all?
Santa and the elves have been employing state of the art technology to deliver to the millions of boys and girls he visits around the world on Christmas Eve.
Norah Patten, Aeronautical Engineer and Business Development Manager with Réaltra Space Systems Engineering in Dublin says that the North Pole has been deploying some of the systems used by the likes of NASA and the European Space Agency when he takes flight.
Ms Patten says: "Santa's Sleigh is actually very high tech. Santa and the Elves use some of the latest technologies that are developed by NASA and the European Space Agency for their rockets.
"For example they use composite materials which are very light weight and very strong.
"They have sensors embedded throughout and these allow the elves to understand the weight distribution of the Sleigh as they pack all the gifts and presents."
The journey: how does he find his way?
Santa has also moved on from maps and no longer relies solely on his reindeers' sense of direction.
AI is also helping him find the quickest route around the globe.
Mark Kelly says: "He uses AI and geospatial data to map the optimal course to ensure he delivers all those presents within the one night."
The duration: Does he really only do it in just one night?
Yes and no. There's 24 hours in a day. However, Santa actually has almost a day and a half to do his deliveries because of a number of factors including the rotation of the earth and the fact that the world is divided into 24 time zones.
As Santa flies East to West he actually has 31 hours in which to deliver presents.
How fast does he go?
Experts say that to visit around 200 million homes it is estimated Santa needs to travel at a speed of more than two thousand kilometres per second.
The greatest minds in science have been studying this topic for a long time to try and figure out how Santa achieves such a feat.
They have yet to come to a scientific consensus on this and only explanation for the way he does that...is magic!
What time will he arrive in Ireland?
The exact time is never clear which is why it is important that boys and girls get to bed and to sleep as early as possible.
The Irish Aviation Authority says they have designed a flight path across Ireland for Santa Claus tonight and the Minister for Transport Eamon Ryan has given his sleigh special clearance to enter and traverse Irish skies for the duration of the night.
Met Éireann says while the forecast for Christmas Eve is cloudy, these conditions should help Santa make his journey safely and speedily across the island of Ireland tonight.
