Idioms

"save for a rainy day" is the only way i've ever heard it

In British (and I suspect American) English it is always 'a' rainy day. We use the indefinite article because the situation being described (a sudden need for money which is not part of the normal budget) is hypothetical and not certain to happen.

I've never heard anyone say "save for the rainy day." It must be a bunch of commies.

Thanks very much. Probably the British and Americans who said "to save for 'the' rainy day" did not care much about their articles. However, all of them were university graduates.