I found this fairly interesting:
Earlier this month, Leland Chee tweeted this:
I II CW III R IV V VI
0 10 10-13 13 27 32 35 36
That's an official canonical calendar for Star Wars, based on TPM being the zero date, including Clone Wars and Rebels. One of the commenters in the thread points out that Palpatine taking power might make a better zero date since it marks a new government system in power for the majority of the SW galaxy, which is an interesting take on it if you MUST have a calendar not based on ANH/the battle of Yavin.
While I think io9 is making a mountain out of a molehill here, they aren't wrong exactly. Adding a second calendar system now is confusing for the existing but easier for newcomers, yet keeping the existing calendar system going as well just makes it baffling for those newcomers to follow 2 systems.
Perhaps the most interesting element though is that Rebels takes place 14 years after Episode III, which means it's 5 years before ANH. Having read A New Dawn, the prelude to Rebels, the back cover says the story takes place some time before the events of the new show, giving Hera and Kanan time to develop a relationship and the rest of their rebel cell before meeting Ezra Bridger. The book IIRC is a bit vague about how much time had passed between the rise of the Empire and its events, but I do seem to remember a hard number somewhere regarding Kanan's age - though the book is also an Advance Reader edition so that could be changed anyway.