Originally Posted by O2pilot

It’s contractual. Its to make sure that we get 24 paychecks each year, and not have some years we get 25 and others 23. People have complained that pushing extra pay into a specific tax year is bad for them, so its evened out by making sure that the Jan 1st paycheck isn’t pushed into the previous year.

Remember that you started 2018 with a paycheck as well just like this one.