Seemingly random days missing from statistics

Background: I am using Anki Desktop Version ⁨2.1.60 (76d88073)⁩ Python 3.9.15 Qt 6.4.2 PyQt 6.4.0 as well as AnkiDroid (automatic update). I keep track of my statistics manually as well as occasionally viewing within the desktop or Android apps. Before creating and account and posting here, I followed all the suggestions on the Anki website, ensured database checked for errors, started without any add-ons, etc. The problem persists on both platforms.

Problem: Sometime in the last week, Anki shows missing (zero data) for the following days on my account when I have manual records (rounded to the nearest minute, not # cards) showing study time: 20220102, 20220104, 20220107, 20220112, 20220114, 20220129, 20220204, 20220209, 20220222, 20221206, 20230120, 20230125, 20230221, 20230301 (YYYY-MM-DD format). I do not know if the issue was due to the recent daylight savings time change (as other forum members have noted). As my manual records do not include cards studied (only time), I cannot verify if there are other errors in numbers of cards studied on other days. Before trying to resolve the issue, I was running Windows version 2.1.54 but updating to 2.1.60 did not resolve the issue. Anyway, I first noticed the problem on AnkiDroid (main study platform) and then confirmed on Anki Desktop.

As I do not know the exact date the incident occurred, I do not want to start randomly restoring from automatic backups unless advised. Any insights are appreciated. Thanks in advance.

You can confirm whether daylight savings is involved by backing up your collection, and changing the timezone set on your computer to one that matches the offset present before the DST change. Do you have a habit of reviewing cards around midnight? What happens if you change your day rollover time to the default of 4am?

OK it does appear to be a Daylight Savings Time change issue, as per your instructions, changing my review time to 1-4hr after midnight has removed all the erroneous days missing. While I do not have a habit of reviewing around midnight, I try to maintain a streak and therefore if I note that I have forgotten to study at 11pm at night (local time) then I will do my reviews, so the missing days must have been those kind of days. For now I will keep set to have new days begin 0100am, but it would be nice if Anki “remembered” internal clock settings for DST at different times of the year. Thank you.

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