2. I don't know: it's hard. After all, birthdays belong to one's privacy. Strangers, especially those with a strong sense of prevention, will not tell you easily. Even if they tell you, it may be perfunctory. So the step is to turn the unknown into the known first, and then ask with reference to the known. If everyone is in the same circle (for example, different departments of the same company), say that you are applying for a benefit, you can send birthday gifts to everyone, and you need to provide your birthday date and so on. )