With the exception of Christmas Day and Boxing Day which are universal there are only two concurrent days that affect parts of the UK's population. One is the Scottish Hogmanney 1st and 2nd January, but these are so close to Christmas that to be honest if you're there or not you don't care what effect these have on you as you're probably off too. The other of course as any N.I.P.P.L.E. will tell you is the 12th and 13th of July.
Like the others listed these are movable in the extent that should they fall on a weekend they will be moved to the start of the next week. The above two mean that wherever you are in the UK, or world for that matter, you'll probably not notice much chance though the festivities, but for the Northern Irish holiday you may notice only if your pay goes into your retained Northern Irish account mid-month.
You see back in 1690 by a quirk of fate King William deigned to do battle at the Boyne on the 12th without thought nor hindrance for 21st century banking practices. The fact that banks weren't universal at the time he sought to right Britain of the Stuart dynasty of his wife is no excuse. That he should merit the same length of holiday celebration as our Lord and Saviour's birth is also not really acceptable. William should really have had better foresight and either delayed his muster for 4 days or got there a day earlier.
The net result of the mustering of the first Irish Orangemen was that the celebrations can be shifted to the 14th and 15th of July should the Twelth surreptitiously fall on a Saturday. In the days of ledger book banking this probably would have had negligible effect as you wouldn't expect the money from your pay to be in your account right on the day you received it. But when you get electronic transfer you expect it to be there soon after midnight on the day in question, 15th of every month. Somehow this does not apply to one July ever 6 to 7 years.
If you live in Northern Ireland and get paid mid-month you employer will have probably arranged for you pay date that July, like this to be advanced to the 11th. However, if you are a N.I.P.P.L.E. you employer does not take this into account and, should you end up to the limit you can take out at the end of the previous pay month, you will find yourself for 24 hours unable to take out cash.
Now should you as a customer fail to have funds when a direct debit is scheduled to leave your account the bank will, at present, change you for this misdemeanor. However, if the bank should fail to allow a N.I.P.P.L.E. their money on schedule what can we do? Should we write to them asking for this and charging them £30 for the privilege? After all that is what they would do. Now surely fairness should lead to a quid pro quou. I know that no individual is actually there transferring my pay into my account every month. So how come once every 6/7 years the little elves of Electronic Banking take a 4 day leave or absence and don't let me access my wages until the 16th July.