If you mean Acharya Siddhisuri, who was popularly called “Baapji Maharaj,” I could not find a clear birth date in the JainKnowledge material I checked. The JainKnowledge page that mentions him mainly identifies him by that title, but does not clearly give a birth year or birth date. ( en.wikipedia.org)

If you meant a different Baapji Maharaj in Jain tradition, the exact name or lineage would be needed to identify the correct birth details.