Page generation issue

[liver121888]

I am in UTC +8 now, assume the local time now is 17:21:00. so I try to post a page in /_posts with the date set to 2022-02-07 17:21:00, but the page does not generate in /_sites/development. so I trial and error the date to 2022-02-07 9:20:59, and it generates the page! but if I set to 2022-02-07 9:21:01, it does not generate... what is the mechanism behind all these? I only know it is somehow about timezones. I am using visual studio code for Jekyll, does this affect the date somehow? A novice in Ruby and internet blogging...