Here's a few tips, courtesy of the BBC:

"Don't give up hope if he doesn't dive into your arms the instant you mention the M word.

But who will spare a thought for those poor dumb chaps who - until the
moment 1 March dawns - will be terrified in case their girlfriend
decides to seizes the day?

And what about those girls whose fellas have been subtly
dropping hints for weeks that it's a leap year, hoping to spur an act
of feisty impulse?
"

Both of them, fear not. Help is at hand.

List of how to handle the situation posted in next box.