The wife got onto this green California kick of eliminating the (gray)
trash can altogether in favor of (blue) recycling and (green) compost.

She seems to think she can harvest her compost by the summer, which she
started on the first of January by daily collecting the household food
waste (bread, pop tarts, cereal, leftover chocolate candies, chicken bones,
fish skin, pizza crusts, eggshells, pasta, too-crisp bacon, etc.) in a
kitchen tupperware container.

Once a day she dumps that into a large green bucket outside, and throws a
pile of soil on top to cover it from the animals and sprays water over the
top to soak it. The green compost bucket is about chest high so the chance
of actually mixing the compost is slim at best.

That's all well and good - but having no experience with compost, I wonder
how long it will take for her to harvest the results.

She seems to think by summer it will be ready.
I think it will take much longer than that.

The question is: How long will it be before compost is usable for
gardening?

Note: We live in the northern California arid climate (it won't rain for 10
months and then in the winter, it will very lightly rain for a few weeks at
a time). Once in a blue moon there will be a downpour - but that's rare so
she'll have to keep wetting it herself.