Using Moodle 3.11+ (Build: 20210611)

with a default server timezone set to Australia/Hobart.

if if view page: /mod/quiz/view.php?id=1902 

i see:

Opens: Monday, 21 June 2021, 9:00 AM
Closes: Friday, 19 November 2021, 11:59 PM

this is the expected result as it was set in the interface.

However, if i edit the quiz: using url /course/modedit.php?update=1902&return=1

The start and end times are offset by 9 hours, this is not expected.

likewise, when i edit the quiz on url /mod/quiz/edit.php?cmid=1902
i see:

which is not expected.

we have changed the user timezone from Australia/Hobart to Australia/Perth (two hours behind) and the times change from 18:00 to 16:00.

so the issue is a timezone problem.

most of the dates in moodle are stored as seconds from 1970-01-01 so i don't think it will affect students, but our issue is if we needed to modify the quiz, we need to be super-careful to change the start and end times of the quiz before re-saving.