For a while, Achievabee could tell you a chore was finished when it was not. Not often, and not for most families, but the failure was quiet and it pointed the wrong way, which is the worst combination.
If you were reading the app on a phone set to a timezone east of your household, the dashboard could show "All done today" for a chore that was still outstanding.
Where the disagreement came from
A chore is due at a moment in time, and that moment is worked out from your household's timezone. You set it once when you create the household, and everything the scheduler does hangs off it.
Two places in the app were not asking that question. They compared against midnight on the device instead.
Most of the time those agree, because your phone is usually in the same timezone as your house. When they disagree, the app is comparing a chore built in one clock against a day boundary taken from another.
A parent would have believed the bed was made.
On a device far enough east, the dashboard read the previous day's chore as today's. So "Make your bed" reported as done while today's was still sitting there untouched. Further east again and it flipped the other way, reporting no chores due against chores that were genuinely due.
The kid's app had a smaller version of the same fault: the same chore could appear under "My chores" and "Done today" at the same time.
Why it took a while to see
Nothing was broken in a way that shows up. There was no error, no empty screen, no red anything. The app answered confidently and the answer was wrong, which is the kind of bug that survives a lot of testing because nobody thinks to check a phone against a house.
It also only appears when the two clocks disagree, so it is invisible at home and shows up on holiday, which is exactly when a parent is least likely to be auditing a chore list.
What changed
Every "is this due today" question now resolves in your household's timezone rather than your device's.
I checked it by running the real code against a household in Los Angeles under seven different device timezones. The old comparison was wrong in six of the seven. The new one was correct in all seven, and then confirmed in both apps against live data.
The part worth keeping
The fix was small. The lesson was not.
A chore app is a clock with a to-do list attached, and every question it answers is really a question about when. Two places in the code had quietly decided "when" meant something different from everywhere else, and neither was wrong on its own terms. They only disagreed with the rest of the system.
I now keep the date comparisons in one place in each app rather than letting each screen work it out. That does not make the next mistake impossible, but it makes the wrong version harder to write by accident than the right one.