Bug with "All day" option

Hello,

I use the last version 5.6, but there was the same bug with a previous version.
It seems there is a bug when the “All day” checkbox is checked.
I have created events : some are for an only day and others are for few days. And there is a -1day bug. For example if I create an event between the 2 september and 10 september into the wordpress admin, on the website : the daily archive pages, it will be shown between the 1 september and 9 september.

I searched a lot why… and i finally found it seems to be linked to hours starting/ending and timezone. My website is UTC+2.
If the starting hour & ending hour are 01:00 (option by default), even “All day” is checked, there is the bug -1day I described above. However, if I turn it to 03:00 to 23:00, the bug doesn’t appear anymore.

So I searched a bit into the code, and I found the wordpress query. There is a problem with timestamp. The starting and ending timestamp hours are something like XX-XX-XXX 02:00:00 and the starting/ending value of my event are XX-XX-XXX 01:00:00. This is a good clue to start I guess.

It’s a bit complex, i don’t know if i’m very clear… but let me know if I can help you. This bug is a bit embarrassing for me, the plugin is installed on a client website.

Thanks.

https://ww.wp.xz.cn/plugins/events-manager/