Question: how to calculate date of birth in numerology?
Answer: Consider your complete birth date. For instance – October 19, 1982.
Bring down the month, day and year to a single digit number by adding them. Month: October, or 10th month. Add 1+0 = 1. Day: Day 19. Add 1+9=10. ... 
Add the resultant single digits to get your life path number.