I'm reading Edgar Snow's Red Star Over China at the moment and he mentions that traditionally everyone was considered to have gotten one year older on the day after Chinese New Year rather than on the anniversary of their birth. However I know from experience that in modern China people celebrate the anniversary of their birth as their birthday. I was wondering if someone could shine some light on whether or not Snow's claim is accurate and if so how birthday celebrations have developed in China over time?
Your birthday is still your birthday and it's not uncommon to celebrate it as you might in the West. However your age is still calculated at the new year. Traditionally that's the lunar new year, so typically the end of January or beginning of February. However the date by which it's calculated has moved to the first of January for most people.
Snow is still correct. What you're talking about is actually two different questions.
When do Chinese typically celebrate their birthday?
When do Chinese typically add a year to their stated age?
What you're seeing is the first question, and the answer is usually "on their birthday". But what Snow is talking about is the second question, which is still the normal way of doing things in China (and Korea and Taiwan).