Do you have four auspicious days?

We divide it into some days, such as happy events, such as opening, wedding and so on. Some people in China like auspicious days, while others don't care. Personally, I don't think there is anything unlucky. Besides, many idioms in our country begin with 4, such as the study of the four seasons, which extends in all directions and is safe. Why use 4? Is that so?