Answer To The Chanuka Trivia

Question can be read here 

1) Becomes Bar Mitzvah not on his(בו ביום) birthday.

2)Born on the same day, (one at 1.00pm the second

on 1.02pm)

One becomes Bar Mitzvah a day earlier than the other.

(Molad was @ 1.01pm)

1) The Mishna Verurah (55 sk 45) writes If someone was born on

Rosh Chodesh  Kislev* that  had only one day Rosh Chodesh and

thirteen years later there are two days Rosh Chodesh (last year )

he becomes Bar Mitzvah on the 30^th day in Cheshvan.

(not on his birthday 1^st. Kislev)

2) The Piskei Teshuvos brings a Shita (אפיקי מגינים)who argues on M.V. and holds

that it depends if the child was born before  or after the Molad. Hence two children

born on a one day Rosh Chodesh Kislev ,one was born before

the Molad and the other after the Molad. Thirteen years later if there are two days

R.Chodesh, the one born before the Molad becomes BarMitzvah on the 30th of Cheshvan.

The one born after the Molad becomes Bar Mitzvah on the 1st. of Kislev. (2nd day R.Ch.)

*or Teves