Sharepoint Date Picker shows the previous day in the list item cell

[Vadocz_Janos]

Dear Community,

I have about 30 similar SharePoint Lists at the company. I saw that SharePoint UI changed in the middle of October, 2023. Since then, in every Date type column where I use a Date Picker, after I selected the date it will put the previous day into the cell. At the same time it shows the selected day correctly in the Excel to where I exported this SharePoint Lists. So it seems that it saves the correct date, but in SharePoint List it visualizes the previous day.

I use UTC+1 time zone, SharePoint lists open in browser, I don't use PowerApps, I didn't change any time settings for the Lists or the Site either (I tried to change it but didn't solve the problem).

Example: as you see, I want to select 2023.10.01., but after the selection it puts 2023.09.30. into the cell (in practice it seems that it puts the selected date in the cell, but milliseconds later it turns to the previous day).
However, in the exported Excel I see the correct 2023.10.01. date.

Thank you for your help!
Vadocz Janos

[#2]

After a month it resolved itself. Now it saves and shows the date I selected in the date picker properly. But this is very weird.
I refreshed all my lists with F5 - I do it very frequently - and all dates changed to the proper value.
As you see the date format changed. And while the 'modified' system column value is the same, the 'Start Date' and 'End Date' editable columns value was added 1 day.

In the meantime one thing happened: today there was an automatic system update. After I rebooted my notebook, it run a memory test and upgraded BIOS. But I can't imagine that this BIOS upgrade is effected on SharePoint list format. I didn't change any Regional Settings in the meantime.