Simplify the following text for a Grade 10 native English-speaking person.
Original: Note : due to the requirement exclusive `` dtend '' in hCalendar , and the accessibility problems that presents when a date is rendered ( as seen without CSS ) as 28 March 1999 ( 1999-03-29 ) or even 28 February 1999 ( 1999-03-01 ) or 31 December 1999 ( 2000-01-01 ) , the Date end template should not be used for whole-day dates and should have a time of 23:59:59 .
Simplified: Note : due to the requirement exclusive `` dtend '' in hCalendar , the Date end template should not be used for whole-day dates and should have a time of 23:59:59 .