And actually the result is pretty close to 0. I mean it’s less than 0.1 year.
I wonder if it might have been better if only integers had been accepted for the components? If you want 0.3 years write 0.3 * '1 year'::interval. But changing it now would be a pretty significant backwards compatibility break.
There's really no avoiding counterintuitive behaviour though. Look at this:
In other words, doing the “same” calculation but with multiplying 1 year intervals by floats to get the values to add, you end up with an interval that while not identical to 0 does compare equal to 0. So very close to 0; in fact, as close to 0 as you can get without actually being identically 0.
