Days count looks wrong or does not match the countdown
Why the list can say 10 days while the countdown screen says 9 days and 16 hours.
Nine times out of ten this is not a bug but two different questions being answered.
The list counts calendar days; the countdown counts exact time
The events list answers the question people usually ask out loud: how many days away is it? If today is Friday and the wedding is a week on Monday, that is 10 days, even though it is 9 days and 16 hours until the ceremony starts.
The event's own screen answers the precise question: exactly how long until the moment, in days, hours, minutes and seconds. So the two can legitimately differ by one while both being right.
Events with no time set
An event without a time counts to the start of its day in your time zone. On the day itself it reads as today rather than showing hours to some arbitrary moment.
Time zones
Dates are anchored to your device's current time zone. If you travel across time zones, counts adjust to local midnight, which can shift a far away all-day event by a day compared to home. That is the count staying honest about local time, not drifting.
If every event is out by exactly an hour instead, check your Home Timezone: see Event times look an hour off.
If it is genuinely wrong
If a count is out by more than one day, or disagrees with the date you set, that is worth telling us about: contact us with the event's date, whether it has a time, and your time zone. In the app, Settings then Contact Support attaches the technical details automatically.
Did this not solve it? Contact us and include what you tried. In the app, Settings then Contact Support attaches the details that help us find your account.