Friendly style

I heard an interesting custom from my Mandarin teacher.
She told me that people in China usually ask their friend's age when they meet for the first time.
I was very surprised because it's taboo in Japan and also in Western countries.
I asked her why. She told me it's important to know whether a new friend is elder or younger. After they know it, they can call their friends elder or younger siblings.
It's their friendly attitude, she said so.
And I also heard they don't use the western calendar when they ask somebody's birth year. It's a little complicated for them, so they usually use the Chinese zodiac. Really!!! I didn't know that!!!