This is first day of the year.

如果是问号，则写What is the first day of a year?或Which day is the first day of a year?一年的第一天是哪一天?如果结尾是句号，则写January 1st is the first day of a year.一月一日是一年的第一天.或New Year's Day is the first day of a year.元旦是一年的第一天.