How to calculate the foreign Gregorian calendar?

Do foreigners have to look at the Gregorian calendar when they get married?

Foreigners don't have a yellow calendar. They use the solar calendar to calculate the years, but they should also choose a good day. When they hold a ceremony, they will go to the church and ask the priest to marry them.

Foreigners don't pay attention to the solar calendar, they think that time is enough, and everything is fine when the weather is good and the mood is good.