With the discussions going on about how to plan and block time for projects, I went back to GTD and looked for more information on the topic.
On page 40 where DA is discussing No More "Daily To-Do" Lists, he says:
"Having a working game plan as a reference point is always useful..."
On page189 where he is discussing Executive Operational Review Time, he says:
"I've coached many executives to block out two hours on their calendars on Fridays [for weekly review]."
So DA does say it is useful to have a plan, and he does advocate putting something on a calendar that doesn't HAVE to be done at that specific day/time.
My question is how does he or anyone else out there mark these things so they are distinguished from the true calendar "have-tos"?