Steps to reproduce the issue

Check any calendar
for e.g. Contents > Articles > Try to edit any article > Go to Publishing Tab > check the calendar here

Issue 1

Hover on dates - date disappears (reason: color is set to white)

Issue 2

Time icon missing

Expected result

Date should not disappear on hover
Time icon should be visible

Actual result

Date disappears on hover
Time icon missing

System information (as much as possible)

PHP 8.0.6
MySQLi 10.4.19-MariaDB
Chrome on Windows 10

pinging @ciar4n