Warning: Season 7 finale spoilers ahead

This weekend's premiere of "Doctor Who" Season 8 has fans anxiously waiting to meet Peter Capaldi, the new face of the Doctor. Capaldi's doctor will be the 12th -- or 13th, depending on how you count John Hurt's The War Doctor -- regeneration of the beloved Time Lord. 

Over the show's 50-year run, the question of how old the doctor is has never been fully answered. As a man with many faces, appearance is no indicator of age. The first Doctor, portrayed by William Hartnell, stole the Tardis at the young age of 236 years yet he remains one of the oldest-looking Doctors. Matt Smith's eleventh Doctor lived 1,196 years and it wasn't until the siege of Trenzalore around his 1,500th year that he began to age.

Executive Producer and writer Steven Moffat insists that not knowing his own age is part of being the Doctor. "The thing I keep banging on about is that he doesn't know what age he is. He's lying," said Moffat in 2010, "how could he know, unless he's marking it on a wall? He could be 8,000 years old, he could be a million. He has no clue. The calendar will give him no clues."

The Doctor may not remember his own age, but Whovians (Doctor Who fans) have certainly kept track. Fans on the TARDIS Data Core wiki have carefully chronicalled the Doctor's age. They have also noted the discrepencies in reports. The classic Doctors (the first eight) follow a consistent timeline with the eighth Doctor calculating his age at 1,009 when he first regenerated and 1,125 by the end of his life. 

However when the new series of Doctor Who premiered in 2005, the ninth Doctor, played by Christopher Eccleston, stated he has "900 years of time and space." David Tennant's 10th Doctor came on to the scene at age 903 and, after searching for Martha Jones for 33 months, gave his age as 906 shortly before he regenerated. The discrepency between the classic and new series has not been acknowledged directly by any of the show's producers. TARDIS data core notes, "It is one of the few notable contradictions of previously established material in the revival. To date no episode, novel or comic strip has addressed the discrepancy."

In the 50th anniversary special The Day of the Doctor, the 11th Doctor cites his age as "Twelve hundred and something, I think, unless I'm lying,” yet he later admits he no longer remembers if he is lying about his age or not. Upon hearing this, the War Doctor remarks they are 400 years apart. This was, of course, before the Doctor defended Trenzalore for 900 years. If we are to follow Moffat's 2005 series, the 11th Doctor regenerated at 2,100 years old. Ignoring the discrepancy between the eighth and ninth Doctor, however, makes the Doctor 2,822 years old.

He's still a baby compared to the Face of Boe, though.

Check out the infographic below to see how old the Doctor really is: