Good eye. Addressed in d02ed22f2aad9043bdb9ffe588f19b2e1b2600d7, where I switch to aggregating based on the actual payday timestamps, not just the date. This made testing a lot easier, too. I added tests for both the "bad week" case you mention, as well as the case of an out-of-band transfer (cf. https://github.com/gittip/www.gittip.com/issues/54#issuecomment-29241396 ff.).