I see this same behavior:
I tried again today and still see the same issue.
On the calendar view, click on a date in the future to create a new event. Here I used February 5th:
The event creation page shows the correct picked date. However, internally, it is incorrectly using today’s date for the start date.
The first clue it is uisng the wrong start date is that if you try to create a reminder for 8 hours before the event, there is a warning that the reminder would be sent in the past on today’s date:
The drop down at the top shows the correct date, but that’s not the date it actually uses when it creates the event as you can see in my linked discussion topic.
You can go back up and try to choose the correct date in the drop down, but it doesn’t change whatever internal date the create event page is using.
Workaround
I did find a workaround that you can choose a different date in the date picker and then set it back to the correct start date.
That cleared the warning message on the reminder:
