I had the same dilemma, how to choose to put some tasks with due date in Nirvana and some tasks in Calendar?
This caused me stress and unreliability.
I asked my official GTD Level 1 coach and he told me that the best thing to do is to have all tasks with due dates in one place.
In other words.
If I decided to use the calendar, I would have to put all my due date tasks on the calendar, that meant both the time-stamped tasks, the dated tasks, and the tracking file.
On the other hand, if I decided to use Nirvana for the dated tasks, I would have to use the Nirvana scheduled list as the calendar, putting there the timestamped tasks, the date-only tasks, and the tracking file.
This was an eye-opener for me, because it avoided having to look in two places and eliminated at once the doubt about what to check first.
In my case, I decided to use Nirvana's "Scheduled" list as my calendar and it was a great success.
I completely discarded the use of the traditional calendar and moved all my events to the Nirvana Scheduled list.
Some will say, that's all well and good, but what happens when you are invited to a meeting? or when you have to call a meeting?
Simple and effective, in the first case, I copy the meeting details into the Nirvana scheduled task.
In the second case, next to the meeting invitees, I put the address of my Nirvana inbox and I get the invitation to my Nirvana inbox which I transform into a calendar appointment in Nirvana.
I hope this has helped you to clarify
Translated with
www.DeepL.com/Translator (free version)