It's the seventh day of the Lunar New Year and it's the people's day, 人曰, hence everybody's birthday.
I wished some friends from China a happy birthday and was surprised when they asked me what it was for. I did a brief search and confirmed that this is generally celebrated by all Chinese including China.
We discussed it and concluded that most people in China may have lost and stopped most of the older customs and traditions, whereas the overseas Chinese having moved out of their ancestral land have made it a point to maintain as many customs and traditions as they can, and as a result still keeping most of them.
My family and I, whilst not deliberately celebrating our so-called birthdays, went out for dinner and it was a very nice time of being together, though it was quite tough to hold conversations in a very, very noisy Chinese restaurant! But we had a good time, and good food nonetheless.