Dunmurderin'

Edited to add perfect icon and correct figures.

Got to watching Cosmos (not the one in the icon) on the internet tonight and saw the episode where Carl Sagan condensed the history of the universe, roughly 13.7 15 billion years worth, into one year to give a sense of the scale of time. You can see a version of the Cosmic Calendar here. (note: the version in the link uses 13.7 billion years for the age of the universe.)

Now, being that it's almost time for me to go to work and I am bored and nerdy, I decided to try and figure out when various events in the Transformers timeline would have taken place (err, the G1 cartoon timeline, that is).

According to the episode ("The Shores of the Cosmic Ocean") the calendar breaks down like this:
1 month = 1.25 billion years
1 day = 40 million years
1 minute = 30,000 years
1 second = 500 years

Using those figures, I determined that a million years is roughly half an hour if you figure 1,000,000/500 = 2,000 and 2,000/60 = 33.33333... (I'll be the first to admit my math may be wayyyyy off so any corrections are more than welcomed.)

Going by that on December 31st (information in italics is taken from the Cosmic Calendar link above; you can read more about the Transfomer-specific events at the TF Wiki's entry about the G1 cartoon timeline) -- Edited once more to correct times, these are my final figures (unless I realize later that they're not)

Origin of Proconsul and Ramapithecus, probable ancestors of apes and men: approximately 1:30 p.m.

The Quintessons establish themselves on Cybertron: approximately 5:24 p.m. (12 million years ago)

The Transformers' ancestors overthrow the Quintessons: approximately 5:54 p.m. (11 million years ago)

Megatron's Creation: approximately 6:30 p.m. (10 million years ago; not entirely sure where I got this figure from)

Events in War Dawn/Creation of Optimus Prime: approximatley 7:00 p.m. (9 million years ago)

The Ark leaves/Autobots & Decepticons stranded on Earth: approximately 9:48 p.m. (4 million years ago)

First humans: approximately 10:30pm (roughly 2.7 million years ago)

Pretenders crash-land on Earth: approximately 11:59:44 p.m. (roughly 8,000 years ago)

Widespread development of science and technology; emergence of global culture; acquisition of the means of self-destruction of the human species; first steps in spacecraft planetary exploration and the search of extraterrestrial intelligence: Now: The first second of New Year's Day -- also when the Transformers Wake Up.

To put it another way: all of human history, from the rise of agriculture during the Neolithic period (roughly 12,000 years ago) to the moment you're reading this right now is roughly 24 seconds long on this scale. The entirity of Transformer history, from the time they rebelled against the Quintessons to the present day is 21,960 seconds long -- or about six hours and six minutes. Optimus Prime is at least 18,000 seconds old -- or about five hours.

Non-G1 Timelines:

In the movie timeline, the Allspark Cube crashed on earth at approximatley 11:59:20 p.m., roughly about the time humans developed agriculture (approx. 10,000 yrs ago) give or take a couple seconds (apparently according to the movie the Cube crash-landed 12,000 years ago).

I checked for other timelines over at the Teletraan-1, the Transformers Wiki, but G1 is one of the few continuities that actually gives 'dates'. For everything else, less definite dates are given ("In Cybertron's Dark Ages" is not helpful).

Addition: Wayward Martian reminded me about "Transformers: The Ultimate Guide" by Simon Furman (a.k.a. the Book of Holy Furman) which has a timeline for events in the Dreamwave comics continuity. Here is:

( Dreamwave Comics Timeline )

And 'cause I found this today: ( IDW Comics Timeline )