Morning @v-siky-msft !!!
Well, I´ve try some variations of the formula and experienced some weird situations......
First try, using CalendarPostItem:
Office365Outlook.CalendarPostItem(MyCalendar;
DateValue(Text(ThisItem.'Appointment Date'))+Time(Value(Left(ThisItem.'End Time';2));Value(Right(ThisItem.'End Time';2));0);
DateValue(Text(ThisItem.'Appointment Date'))+Time(Value(Left(ThisItem.'Start Time';2));Value(Right(ThisItem.'Start Time';2));0);
"Test”;{StartTimeZone:"E. South America Standard Time";EndTimeZone:"E. South America Standard Time"})

Odd facts.....
Even with the times fixed in the sharepoint, he is creating the event with 3 more hours according to the time zone ...... which doesn't make sense since I don't want him to add hours, just create with this timezone.


Second try....
Office365Outlook.V4CalendarPostItem(MyCalendar;"Test";
DateValue(Text(ThisItem.'Appointment Date'))+Time(Value(Left(ThisItem.'Start Time';2));Value(Right(ThisItem.'Start Time';2));0);
DateValue(Text(ThisItem.'Appointment Date'))+Time(Value(Left(ThisItem.'End Time';2));Value(Right(ThisItem.'End Time';2));0);
"(UTC-03:00) Brasilia")
Nothing Happend!!!! Even without erros…………….
Third try…..
Office365Outlook.CalendarPostItem(MyCalendar;
DateValue(Text(ThisItem.'Appointment Date'))+Time(Value(Left(ThisItem.'End Time';2));Value(Right(ThisItem.'End Time';2));0);
DateValue(Text(ThisItem.'Appointment Date'))+Time(Value(Left(ThisItem.'Start Time';2));Value(Right(ThisItem.'Start Time';2));0);
"Test”;{StartTimeZone: "(UTC-03:00) Brasilia";EndTimeZone: "(UTC-03:00) Brasilia"})
Nothing Happend!!!! Even without erros…………….
Fourth try…
Perhaps the most complex attempt ..... I removed part of the formula and put it in a label to make it easy ..... start and end date and time went to lblStart and lblEnd
Office365Outlook.CalendarPostItem(MyCalendar;lblEnd;lblStart;"Test4")

This time I didn´t set any timezone......the result.....
Bingo.....it creates the appointment, and at first at the same time as this on the sharepoint ......

But, when I open the appointment, the times are different from the one shown on the main screen!!!!
What a F……..how odd is that?

@v-siky-msft, in fact the solution that you provided it could be perfectly executed for those who are in UTC, if you prefer, I can close this post with the solution that you gave and open another with this time zone discussion, or what do you think?
George