The Ben 10 series included the original series in 2005-2008 (Ben Tennyson is 10 when it begins) and the series Ben 10: Alien Force from 2008 to 2010 (Ben Tennyson 1s 15).
It is probably sometime from the 1st to 9th of October because in the new Ben 10 (omniverse) it starts in august and he is still 16. Every series he usually ages a year and in the original it is set in the summer holidays and their is a Christmas episode and he would have mentioned also it has to be from 1st to 9th because its from September end of original series) to 10.10.10 (ultimate alien starts.)
Actually, it doesn't say anything about Ben's birthdate. He's just ten-year old Benjamin Tennyson with an alien omnitrix.
The first episode aired on December 27, 2005.
As the name implies Ben 10 is 10
December 27, 2005 .
2005
Ben Williamson - footballer - was born on 1988-12-25.
Yes! In fact, Gwen's name is Gwendolyn Tennyson and Ben's is Benjamin Tennysonand the both called Grandpa Max Grandpa and also Gwen calls Ben's mom Aunt Sandra. In Ben 10 Alien Force there is an episode which telss Gwen is Ben's cousin.
He's in Ben 10:The negative 10.he's also in the beginning of Ben 10 Secret of the Omnitrix
Ben Domenech was born in 1981.
Ben Doller was born in 1973.
Ben Whittaker was born on 1989-10-10.
Ben Allan was born on 1968-10-10.
ben Wallace was born on September 10, 1974
Ben Burnley was born on March 10, 1978.
Ben May was born on March 10, 1984.
Ben Amos was born on April 10, 1990.
Ben Sahar was born on August 10, 1989.
Ben Hinchliffe was born on 1988-10-09.
Ben Sinclair was born on 1991-10-01.
Ben Haverkort was born on 1961-10-27.
Ben Gill was born on 1987-10-09.
Ben Kopec was born on 1981-11-10.