Regarding using a '0' date.
This is something that has vexed many fans and I think Japanese superfan abtr (an amazingly dedicated fan) found an elegant solution a few years back that makes for remarkably easy to utilize reference source.
As usual, something I found years ago, tables are far and above the best way to organize data and abtr proved it once again in his(?) timeline:
http://www5b.biglobe.ne.jp/~ryu-tn/onepiece/op.ch1.html
Note that he(?) simply uses two reference points on the far left. One is white and that represents the death of Roger as Year 0. That is to say, this presents the year probably as the people within the world of One Piece currently interpret it: The Great Age of Pirates. Originally I scoffed at the idea that the world would name itself after a scourge that the WG wishes it could extinguish but as of now we have nothing else to go on and until we're presented information to the contrary, it is one of the best options.
The other option is, actually as suggested in this thread, viewing the timeline as the start of Luffy's adventure as Year 0. This reference point is extraordinarily useful when looking at events in the last 50 or so years. They make character relations and positions very easy to see compared to the start of Luffy's journey.
Some people might see it as muddled but if you're looking for raw data that's fast and accessible there's no better way to organize it I'm aware of. Of course I'm all in support of trying new techniques so this is cool! But if I were to go back and update my own (which is not going to happen in a long time if ever because #life) I would definitely follow that pattern until we hear otherwise from Oda.
As far as whether Oda will ever reveal a timeline, he has the ideas but as you can see, it's a messy business. Oda has…on at least one occasion I know of...been extremely (read:extraordinarily) lucky when it comes to planning his timeline. There are definitely details he has in mind but, as you might guess, he has a very busy mind and every once in a while...oops! We're lucky he's so good at BS...I mean explaining things that only look like errors in timeline continuity.
Strong World and Z make me doubtful that he'll ever create a timeline for the current adventure.
The first half is....um...fairly straightforward. There are a few times in East Blue where it's just plain uncertain how much time passed here/there but in the New World the moment he introduced us to the White Strom all that careful counting goes down the drain. Those panels could have taken moments, or they could have taken days depending on how much canon/filler he does/doesn't want to include. Hell, even the skip between Chap 654 and 655 could be an entire arc!
These are the kinds of things one has to consider when dealing with this material on an official basis. It's splitting hairs and it might not seem logical but the golden rule is, If Oda didn't say it, it's Schrodinger's Luffy. That's largely why I've abandoned the idea of timeline work for now but work like this certainly gives us a strong grasp of the progression of day to day events transpiring during the journey!