Even in real life ...most longtime couple actually didn't actually bother picking some sort of cliche special day for confess or propose ...if anything just using that kind day for announce about it ...The whole "I'll confess on (holiday/special event)" thing always felt so arbitrary to me. Wouldn't people usually want to confess before the special event so that said event is even better? I guess it just presents a timeline for the story beats or something
And even in so many romance or non romance series ...waiting for certain special cliché day to confess/propose are very clear red flag and something BAD are 100% to be happen