Tasks with different calendar times

FilipeCuango 

That's because you've given Activity 2 a duration of 1 day which is 3.67 hours and if Activity 2 starts one hour later than the normal start time of 9:00 AM, that 1 day duration will push Activity 2 into the second day.

I would not create a separate calendar for the special tasks that start one hour later. If those special activities are indeed dependent on other tasks (i.e. Finish-to-start relationship) put a lag in the Predecessor (i.e. Activity 1 + 1h).

As I noted, for the type of scheduling you are doing I would avoid entering task duration in days or even hours since rounding will cause problems with the display. I'd enter all durations in minutes. That will give the cleanest and most accurate presentation.

John