When was Saint Gabriel born?

The original Gabriel is regarded in the three Abrahamic faiths as an angel, not as a mortal person. Therefore, Gabriel was never born, since angels are believed to have been created in heaven, not born. Gabriel is particularly important in Christianity and Islam: in Christianity because it was Gabriel who spoke to the virgin Mary; in Islam because it was Gabriel who dictated the Koran to Muhammad. As a namesake, Gabriel has been a very popular name for both male and female saints (Gabriel, Gabriela and Gabrielle are some of the feminine variants). A link to some of them is listed below.

Saint Gabriel the Archangel was not born. He was created by God in Heaven.
He wasn't. He's an angel of God.