Birth number

[mekiac]

I have a brilliant idea: I'll go on a 80 year-long journey in a region full of junctions and trap dors and I won't take a map with me!
Sounds like you? Naah!

Let's take a random birthdate:
24.05.1978
and add the numbers (same order, random pluses):
2+4+0+5+1+9+7+8 = 36 -> 9 (3+6; cross sum)
and again:
24+05+1978 = 2007 -> 9
and again:
24+05+19+78 = 126 -> 9
2+4051+978 = 5031 -> 9
240+51978 = 52218 -> 18 -> 9
240+51+978 = 1269 -> 18 -> 9
2405 +1978 = 18 -> 9
2+40+51+978 = 1071 -> 9
..... math is boring (when you already know the answer). But life ain't!

I'm just teasing; see for yourself.

Best wishes

[apokalypse]

24.05.1978
and add the numbers (same order, random pluses):
2+4+0+5+1+9+7+8 = 36 -> 9 (3+6; cross sum)
and again:
24+05+1978 = 2007 -> 9
and again:
24+5+19+78 = 126 -> 9
240+51978 = 52218 -> 18 -> 9
240+51+978 = 1269 -> 18 -> 9
2405 +1978 = 18 -> 9
2+40+51+978 = 1071 -> 9
Best wishes

i get all of those 9 for my birthday except for 2+2051+978 = 5031 -> 9 because i don't understand why how have 2+2... for the first 2 digit..

[mekiac]

i don't understand why [...]
Because I made a mistake. A perfect one :p
Haha, nevermind. I corrected it. Thanks

btw: Everyone gets his/her own birth number. It's not always '9'.