Thank you for your response,
I want to show my 'Start Time' of excel on power apps calendar. But it is not showing any circle on calendar for excel Start Time value.

I want to show all Start Time of gallery on calendar(on MonthDayGallery's by using visible Circle )

and filter the gallery by date selected on calendar in power apps. so that all Start Time of gallery(excel data) should be visible on calendar like below

here i used share List named-'YL' and 'Start date' is date column
for this i filter my gallery table first by visible property -Filter(YL,'Start date'=_dateSelected)
and
my MonthDayGallery's Circle by visible property - !IsBlank(LookUp(YL,'Start date'=DateAdd(_firstDayInView,ThisItem.Value, TimeUnit.Days)).Title)
hope you can understand what i mean to say.