Comment 0 for bug 1812560

Calibre 3.38.1 (official download)
Lubuntu 16.04 32-bit (up to date and still supported)

-Steps:

1) Set the date display format to "iso".

2) Try editing the date.

-Results:

A) For standard columns:
  I) in the main interface, the date cannot be modified at all;
 II) in the edit metadata dialog, the current month and year are shown, instead of the actual date; month and year alone may or may not be modifiable: I have not attempted for fear of data corruption.

B) For custom columns, attempting either way of editing results in the date being shown as "i15o" and such.

-Partial user workaround

Set the date display format to "yyyy-MM-ddThh:mm:ss", instead of "iso".

-Postface
 (or, why did I want to edit the ISO date and time, anyway?)

In order to file my previous bug report (1812539), I had to switch my time zone a few times from CET to UTC, and back. Upon finally returning to the original time zone, I noticed that some of the dates (perhaps even many or most; I can't check, lacking a recent backup) had gone back a day (which may be a bug in and of itself, but one I'm presently too lazy to report separately). Since CET is one hour (or two, during DST) ahead of UTC, I surmise that the affected dates where those with time 00:00:00.
The purpose of editing the full ISO string was to try to prevent this from happening again.