Today, 12 Rabiul Awwal Hijriah according to popular opinion is the birthday of prophet Muhammad pbuh. The other is 8 Rabiul Awwal. No matter what the date is, the important thing is that we love our prophet so much for the sacrifices he did for us and we know he too loves us very much. As mentioned in the Qur’an on the last two verses of Surah At Taubah (The Repentance);
Grievous to him is what you suffer;
[he is] concerned over you and to the believers is kind and merciful.
there is no deity except Him. On Him I have relied,
and He is the Lord of the Great Throne.”