yea, i see what you're saying but i'm not sure i'm using the calendar right. for me, even if something goes on your next actions list, most times there can be some type of date associated. Having the to do asap is different than having a 'has to be done by'. to me, way more importance is with the latter. For example, i am going to a friends birthday on october 27th. I need to get him a present. technically this is to do 'asap'. however, the reality is, assuming i order online, I have to allow for shipping and then wrapping so I need to arbitrarily have a must order by to ensure I get his present on time. In this case, let's say I want to get it no later than Oct 20th, this would mean I would have to have it ordered by say Oct 17th. While I think it's valuable to add a calendar date on 10/17, this would be breaking the GTD criteria for using the calendar. If on the other hand all i do is keep it on an to do asap list, and I procrastinate or get caught up in other priorities, I might not realize until 10/26 that I need to get a gift and then it's too late. I don't agree with the idea of having a to do asap list without having some kind of due date.
I don't agree with the "to do ASAP" concept--and I realize that it's probably not your phrase, but somebody else's, maybe out of the GTD book and I didn't like it and therefore rejected it from memory. I would call this category "to work on now". To me, active actions are what I'm working on now. That doesn't mean that they have urgency, it just means that I'm working on them now. It probably means that they're higher priority, though that priority may be as simple as "This would be fun. I'll choose it."
Items that have a higher urgency but little priority (for example, planting peas this September--see what month it is now?) may never make it to the active lists. So urgency is different from priority. But it would be nice to make conscious decisions about urgent items--I would be happier if I had said, flatly, "Peas this fall? Nope."
So how do you make sure that you see urgent items in time to make a conscious decision about them? I'm not referring to items that happen ON a particular day/time--those get the calendar. I'm referring to the NO LATER THAN items. The goal is a system that you trust to tell you, even in a frantic work crunch, and in a way that you will notice, that now is the time to decide whether you're going to order Fred a birthday present.
I think that in the end it's about prioritization and culling. I'm not sure if the exact mechanism that makes those items announce themselves--start date, due date, ticklers, labels, flags, special context, list, calendar, not calendar--matters. I think that what matters is keeping the number of things low enough that you--not some other person with different tolerances for list lengths, but YOU--will notice them when they matter.
At least, that's what matters for me. For someone else, what may matter is forming an unbreakable drop-dead habit of sitting down with a list and a caffeinated beverage, maybe once a week or once a day, and going through a longer list with a clear head. But even then, if the list has a hundred items on it, you have to cull it to the ones that you'll actually do.
But whatever the method, I believe that urgency is a separate issue from the normal workload of projects and actions, and it needs different handling.