Character age list, as requested
Below is a listing of canon character ages and dates of birth (by date, not age!).
Maito Gai: Thirty [January 01st]
Haku: Twenty [January 09th]
Gaara: Seventeen [January 09th]
Aburame Shino: Seventeen [January 23rd]
Tayuya: Nineteen [March 15th]
Yakushi Kabuto: Twenty-four [February 09th]
Tenten: Eighteen [March 09th]
Hyuuga Hanabi: Twelve [March 27th]
Haruno Sakura: Seventeen [March 28th]
Akimichi Chouji: Seventeen [May 01st]
Kankurou: Eighteen [May 15th]
Uchiha Itachi: Twenty-two [June 09th]
Yuuhi Kurenai: Thirty-two [June 11th]
The characters listed below will be turning a year older than what I have listed when it hits their birthdate. So, come July third, Neji will be turning seventeen, and...yeah you get my point.
Hyuuga Neji: Sixteen [July 03rd]
Tsuchi Kin: Nineteen [July 06th]
Inuzuka Kiba: Sixteen [July 07th]
Hagane Kotetsu: Twenty-eight [July 21st]
Uchiha Sasuke: Sixteen [July 23rd]
Tsunade: Fifty-four [August 2nd]
Temari: Nineteen [August 23rd]
Abumi Zaku: Eighteen [September 14th]
Hatake Kakashi: Thirty [September 15th]
Nara Shikamaru: Sixteen [September 22nd]
Yamanaka Ino: Sixteen [September 23rd]
Uzumaki Naruto: Sixteen [October 10th]
Asuma: Thirty-one [October 18th]
Anko: Twenty-eight [October 24th]
Orochimaru Fifty-four [October 27th]
Jiraiya: Fifty-four [November 11th]
Rock Lee: Seventeen [November 7th]
Kamizuki Izumo: Twenty-eight [November 25]
Hyuuga Hinata: Sixteen [December 27th]
Konohamaru: Thirteen [December 31st]
Also, if you don't see a character listed here, that's because they have no canon age/birthday--in such a case, it would probably be best to guess. If I missed a few who do have canon ages...well, I'll fix that later.
Maito Gai: Thirty [January 01st]
Haku: Twenty [January 09th]
Gaara: Seventeen [January 09th]
Aburame Shino: Seventeen [January 23rd]
Tayuya: Nineteen [March 15th]
Yakushi Kabuto: Twenty-four [February 09th]
Tenten: Eighteen [March 09th]
Hyuuga Hanabi: Twelve [March 27th]
Haruno Sakura: Seventeen [March 28th]
Akimichi Chouji: Seventeen [May 01st]
Kankurou: Eighteen [May 15th]
Uchiha Itachi: Twenty-two [June 09th]
Yuuhi Kurenai: Thirty-two [June 11th]
The characters listed below will be turning a year older than what I have listed when it hits their birthdate. So, come July third, Neji will be turning seventeen, and...yeah you get my point.
Hyuuga Neji: Sixteen [July 03rd]
Tsuchi Kin: Nineteen [July 06th]
Inuzuka Kiba: Sixteen [July 07th]
Hagane Kotetsu: Twenty-eight [July 21st]
Uchiha Sasuke: Sixteen [July 23rd]
Tsunade: Fifty-four [August 2nd]
Temari: Nineteen [August 23rd]
Abumi Zaku: Eighteen [September 14th]
Hatake Kakashi: Thirty [September 15th]
Nara Shikamaru: Sixteen [September 22nd]
Yamanaka Ino: Sixteen [September 23rd]
Uzumaki Naruto: Sixteen [October 10th]
Asuma: Thirty-one [October 18th]
Anko: Twenty-eight [October 24th]
Orochimaru Fifty-four [October 27th]
Jiraiya: Fifty-four [November 11th]
Rock Lee: Seventeen [November 7th]
Kamizuki Izumo: Twenty-eight [November 25]
Hyuuga Hinata: Sixteen [December 27th]
Konohamaru: Thirteen [December 31st]
Also, if you don't see a character listed here, that's because they have no canon age/birthday--in such a case, it would probably be best to guess. If I missed a few who do have canon ages...well, I'll fix that later.