What is Damon and Stefan age gap?

There seems to be an error somewhere.

Lily Salvatore died (was turned) in May 1858, which would make Damon 18yrs 11 months and Stefan (born November 1847) 10yrs 6 months. There are three different birth dates for Stefan, November 1846 with two different days in November and November 1847. As Stefan celebrates 162 years in 2009, that would make his birth date 1847. That still makes Damon 18, almost 19 (if Damon was born June 1839).

Throughout the series we are led to believe that when Lily dies, Stefan is 10 and Damon 17. I cannot seem to get this to add up. That would mean Damon was born 1840 and not 1839. Also what doesn't add up is this: we've established that Stefan is 10 when Lily dies in 1858 as this is mentioned. This would mean his birthday is 1847. If this is the case, if he is turned by Katherine in September 1864, he would only be 16 years old, almost 17. As Stefan tells Elena he was 17 when he turned, this would suggest that Stefan was born 1846, making him 11 when his mother dies.

Somewhere in the writing of TVD, an error has been made. The ages don't add up. If he was 17 in 1864, how can he celebrate being 162 in 2009? That would make him 163. Therefore we know he was born 1847, making him 16 when he was turned in 1864. Someone somewhere has really messed up these dates.

Is Damon older than Stephen?

How much older is Damon than Elena?

How old is Damon in human years?