MUTANT MAYHEM TURTLE AGES CONFIRMED
this is a product of insanity on my behalf (no spoilers)
so to start things off the official TMNT Twitter posted this birth month chart for funzies, but I as someone who will never not take things as the factual truth, had to dive deeper.
WHAT DO WE KNOW
1. The movie and trailer both state that the turtles and splinter were mutated "15 years ago". So they are AT LEAST 15
2. The turtles have a confirmed age order being Leo>Raph>Donnie>Mikey (Don's description didn't mention his age but we can assume)
3. Splinter mentioned that when they were mutated they became the age equivalent of when they were animals (grown rat to grown rat man, baby turtles to turtle toddlers).
4. We now know what months they were born in.
WHAT DO WE DO WITH ALL THIS??
Well first we use rationality, if Leo's birthday is first but he's the oldest he must be at least a year older than Mikey and Donnie. We also know that 2008 was 15 years ago (... insane.....). With both of these we can assume that Leo's birthday is sometime January 2007, Raph is April 2007, Don is February 2008 and Mikey is March 2008. Thus making Leo and Raph 16 and Donnie and Mikey 15.
but why stop here...
See knowing the years they were born is the easy part, I want to know the age equivalent of when they were MUTATED. So for those who are curious please stick around
So, it is widely accepted that these four are musk turtles, musk turtles have a lifespan of about 30-50 years, roughly half the average person. We can also assume that the turtles were mutated in August 2008, given that is the same month that Superfly was born.
So let's say the human equivalent age is half of a turtles age (80-100 is roughly double the average 30-50 year turtle life span). Given that 1 year of turtle time is = .5 of human age we divide the turtles technical age PRE MUTATION by two (as before they were mutated they were developing like normal turtles). Leo would be 1 year 7 months in August 2008 assuming he was born in January 2007, so when he was mutated he was the equivalent to a 9.5 month old infant, For Raph he would have been 16 months pre mutation giving him the developmental age of about 8 months. Donnie would be at 3 months and Mikey at 2.5 months old in human development.
So with all that we could probably assume that the boys mental age is slightly less than their actual physical age. To calculate this we would take their developmental age post mutation and add 15 years (since August 2008) making them all 15 with a couple months difference.
To be fair none of this makes sense and I'm totally just running off a whim and got bored and wanted to do some math. But hey if you guys enjoy it
CONCLUSION :
the turtles are 15
TLDR: I did a shit ton of math to prove what we already know and was blatantly stated but with a little more nuance.