If everyone experiencing this bug would write a feedback to Apple following this link
maybe they would fix it...?
Nope, this bug has been known about for well over a year and they have done absolutely nothing. From this, one can only draw two possible conclusions:
1) Apple does not have programmers sufficiently talented to solve this problem
2) Apple consider the cost of fixing this bug to outweigh the benefit... in other words, there's no financial incentive.
If it's point 1 (which I sincerely doubt), then there's no hope and the "just works" slogan will start to sound rather hollow. If it's point 2 (much more likely) then nothing short of an adverse media campaign will get them to turn around.
To be honest, who cares? The only all-day events you might have are April Fool's Day, Easter Monday, maybe the birthday of a loved one or maybe some really important all-day appointment you don't want to miss. All of which is inconsequential to Apple's bottom line.
No, of course I'm being sarcastic - this is unacceptable. Call this out and bring the shame down until they get this sorted out.
From other threads it seems like there is a resolution.
Delete any all day events on the 1st of April, this is causing an issue with time adjustments from Easter clock changes.
My calendar is working again after this fix.
This is not a resolution, it is a workaround that involves me deleting appointments from my Calendar (including a UK religious holiday, no less). A resolution would be for the software bug to be fixed.
As I just commented on another thread relating to this issue, please contact Apple directly either via the Feedback section of their website or via technical support (and ask the techie to report up the line to an engineer). Apple does not read these forums, they exist merely as a place for background chat and for users to swap helpful ideas. Appealing to Apple directly is the only way to exert some kind of pressure in the hope of a potential fix.