I saw some very strange behavior around dates on tasks that seemed to happen around the flip from 2025 to 2026, although I really can't be sure exactly when and how it happened.
It can be best be described as repeated future dates suddenly flipping to a past date. The exact way this happened is not entirely consistent. Let me try to provide some examples.
I have a set of tasks under a heading "Count". They basically count the days in a five day cycle from 5 down to 1, with an extra task called "Zero" that also falls on the same day as 1 (don't ask). I just set these the day before yesterday, so most of these never had a December date (as far as I remember, see additional comment below). They are repeating but most were starting in January.
Yesterday was "Day 5". Today as I writ e this (Jan 1) is "Day 4". I have a filter set up so that I only see the tasks that are for today or for some reason overdue. Yesterday I was only seeing Day 5 as expected, and before the day ended I checked it off so nothing was visible.
This morning, most (but not all) of the dates seem to have reverted back a cycle.
Notice that Day 5 (which was checked off as of yesterday before midnight and moved into January) is now back at yesterday. Day 3 is unchanged. Day 1 and Day 2 have both regressed a cycle into December which I believe are dates they never originally experienced. As an additional interesting detail, I had actually deleted Zero yesterday, and it's back with a December date. Note that I can't be 100% sure about the statement that the "December" dates here were never previously experienced. I don't remember fully if I created them originally with those dates and then checked them off, or if I originally created them with January dates to start.
I checked the version history. Not sure if it is helpful. The last change from yesterday is there at 11:37 PM. It shows some changes I remember making (which by the way, there seems to be some reversion of previous changes I had made which I think is a separate issue). I do see this, which seems to show some thing happening?
Trying to understand this pattern, the last entry in the version history seems to show that things are "repeating" backward in time to the previous iteration when the new iteration should have crossed over the year boundary. Also note that I never actually saw things pop up yesterday in the past. I only actually saw it this morning.
I am on the beta of the web app:
Also, don't know if this is interesting or not... I have been correcting things this morning and you'll notice it says it synced 6 minutes ago. But the version history does not show any entries from this morning:
Separately, it seems I lost a significant amount of changes yesterday as well in what would appear to be a repeat of the sync bug. Various tasks that were created are gone or reverted to an earlier version. So I'm not sure if this is perhaps related. The "regressive dates" might just be a situation of data loss in sync, or it might be something new. If it is just a manifestation of the other bug, then it went quite far back in time this time on some of these items, so I am inclined to think this is actually different but happened to be seen at the same time. (Note that I am only running one instance of the app in a browser. I have it installed on my phone but I have not opened it for perhaps a week.)
I exported the data in this document as a json and edited out other stuff besides the "Count" tasks (although I see this same thing on various other ones). I am attaching it. Also saved the last version history entry as well (unedited). The form does not seem to want to let me upload either json or a zip file. I can send it to someone if you want it.