How would he know his own birthdate? I have always relied on the memories of others.
However you learn your birth date, you usually know it by the age of 49. That was my point: that by nearly 50 yrs of living, the average Joe knows what day his B-Day falls on. Obama still gets confused. Either he’s (1) senile, (2) brain fried, or (3) ineffectively juggling two different dates, take your pick. [I’ll take ‘3’ for Lying Kenyan, Alex.]