$BIGBILL comes at a fixed day each month, but $PAYCHECK happens on a different day every two weeks. Some months, $BIGBILL comes right after $PAYCHECK, in which case you're safe. Other months, $BIGBILL comes right before $PAYCHECK which means you need to find some extra money to cover the period between the bill and your paycheck. If you're living paycheck to paycheck, you always have to have these unsynchronized-cadences in the back of your mind.

This sounds terrifying. It seems like you need a behavioral solution, not a technological solution. Spend a little less, cut where you can, and save until you have a buffer. Then you don't have to worry about paycheck timing.

Welcome to the Bay Area.

That's not just the Bay Area. That's living paycheck-to-paycheck, and it happens everywhere. Sometimes even to "wealthy" people, if they find themselves cash poor (money tied up in retirement, home equity or other property, or investments).

Exactly. If you have a steady income, there's no reason you shouldn't be working on a buffer to separate yourself from bills by at least a month.

Or horribly expensive daycare for two kids :)