Bernard Siebens
0223383c9d
_monthly and signup_split approximated "N months ago" as N*30 days, which drifts against real calendar months by several days a year. Late in some months that drift undershot a full month, so the "dense 13-point series" tests flaked depending on which day they ran (confirmed: every 28th+ of most months). Switched to dateutil.relativedelta for exact calendar-month arithmetic, which is stable on every day of every month.