Ok, let's lay out the facts.
Obito is "killed" during the war, it doesn't matter what age he was. We know he is Kakashi's age, give or take.
Naruto start year; ie. first episode
Naruto 12
Sasuke 12
Itachi 17
Kakashi 26
The events of Itachi killing the entire clan happened 5 years before the start of the series;
Kakashi 21
Naruto 7
Sasuke 7
Itachi 12 (he bested his entire clan when he was 12, the same age Sasuke and Naruto would barely piss without assistance)
The events of Tobi/Obito's attack on Konoha happened 12 years before the start, when Naruto was born:
Kakashi 14
The chuunin exams happened around the same time I would assume, to team 7, ie. when they were 12. This means that the war, Tobi's death and revival all happened during the 2 year period between the chuunin exams and Tobi's attack.