Today I realized that literally all my life-long reviews from the Japanese profile are on one same day. I am not sure the steps to reproduce that other than using 2.1.37 and performing a database check.
The database check code has not changed recently. Did you confirm that restoring from a backup+running the DB check again causes the same issue to occur, and have you ruled out add-ons?
Yes without add-ons. I did some maintenance after updating to .37. Basically I just deleted some add-ons, card types and fields of one note type. I am redoing every step one by one and checking the stats every time. It will take a while as there are +30 iterations in order to discover which step is creating this issue.
Notice I updated from 2.1.22 on that profile.
My hypothesis is that all revlog date changed back tot the current time, as I did that maintenance some days ago (same day as the stats do show) but I didn’t noticed.
I did not reproduced this again. I guess deleting some of the add-ons may have created this. I would need to reinstall the add-ons to be able the reproduce it. Unfortunately, I don’t remember which ones I deleted (not just disabled) exactly, there were like 10-12, and likely versions outdated for >2.128.
I can’t think of anything in Anki’s code that could cause this, as no operations modify existing review times. While it’s not impossible that a bug has slipped in, I think an add-on is the more likely explanation. If you do find the problem reoccurs and can narrow it down, please let us know.