It took quite a while! There have to be the right number of days in the month and the month has to start on the right day of the week for it to work.
Every 28 years
My maths is probably totally wrong, but I did :- leap year = once every 4 years, x 7 days in a week, 4x7=28, add to 1992
Next puzzle:-
Which group of letters is the odd one out?
FDB............YRG.......... MEQ............IHA ............OLC
I am going with OLC
Don't ask how I landed on that
YRG has less dots behind it?
I could make an argument for MEQ, though I have no idea if my reason is the one that the puzzle creators had in mind.