How long is the interval between the events of Kick-Ass and Kick-Ass 2? I believe that Mindy is said to be 15 in the sequel. Do we know how old she was in Kick-Ass?
How about in the comics?
The question of how much time has elapsed since the events of Kick-Ass is answered early on in the sequel in a news report that Dave and his two buddies watch on TV:
They may wear costumes, but it isn't Halloween. They're real life superheroes and in the two years since the first ordinary citizens donned capes and masks, the movement has started to spread.
To also answer the question of the ages of the protagonists in the films and the comics …
"The obvious difference is that I'm older now, and the difference between 11 and 15, which is how old I was when we finished, is that you're a different person, obviously," she offers. "You're calculating more ideas, you're experiencing more things in your own life, you're not just living through other people's eyes, you're making your own decisions. So I was able to step into the sequel knowing that after the first movie I was able to have such an amazing career. I've been able to do such amazing, emotionally stretching things that I didn't just want to do a role like the first one. The first one was great for an 11-year-old, but now I'm older and I want to try something I can sink my teeth into."
Chloë herself was 13 when Kick-Ass came out and 16 when Kick-Ass 2 was released.
Dave's age, on the other hand, is only an estimate. Based on the fact that he is a senior in high school in the sequel, he was probably 15/16 in Kick Ass and 17/18 in Kick-Ass 2. Contrast this with the actor who portrays him, Aaron Taylor-Johnson, who was a believable 20 and an unconvincing 23 year old (with a 46 year old wife to boot) when the two films came out.
I'm not sure about the comics; I don't read them. But for sure, its completely different, considering Mindy was not 15 in the comics, but was rather the same age as she was in Kick-Ass (1). I think it was mentioned somewhere that Mindy was 12 in the first movie. That makes the time-skip more or less 3 years. Besides, it also fits the movies; the first Kick-Ass was released in 2010, and the second 2013.
To me, the film takes four years after the first one because it (Kick-Ass 1) was filmed in 2008 when Chloe Grace Moretz was 11 (Hit Girl's age was based on the actress's) but released in 2 years later in which Chloe was already 13. Kick-Ass 2 was filmed in 2012 (four years after the filming of the first one) and Chloe was 15.
Also, in a deleted scene in Kick-Ass 2, when Kick-ass was asked by a reporter since when did he become a superhero he says "Since I was 16" and in the scene where Katie breaks up with him, Katie's friend Erica says to Dave "Fifteen ditching 20, pervert!".
And for the reporter saying it's been 2 years since the first ordinary citizens became superheroes, I think it's something they forgot to change in the script because if it was really 2 years after the first movie, Kick-Ass and Hit Girl would have been 18 and 13, respectively.