Dear Rabbi Simon,
Now that I am finished geirus, should I or am I allowed to celebrate my secular birthday, or should I only mark it by the Hebrew birthday milestone date (which I am assuming is the date of my Mikvah)?
Thanks,
Mikki
Dear Mikki
Thank you for your question.
It is nice to mark/celebrate the anniversary of your (first) mikveh experience, but there is no impediment to (continuing to) do the same for your birthday in the conventional sense, if you would like to do so. There is still a place forהכרת הטוב (gratitude) for the fact that you were brought into the world on that day. You probably know that many Jewish people mark/note/celebrate their birthdays on the Jewish calendar rather than the civil (Gregorian) one. (Some do both—or even all the days in between.) So, there are a range of valid options. Ultimately, do what feels right to you. However (as implied by your question), IMO there is something very special and meaningful about the Hebrew date on which you joined the Jewish People—of your own free will.
Best wishes
Rabbi Rashi Simon