"A year has 12 months" 用英语表达为 "A year is made up of 12 months."
这个短语的来源是由"a year" 和 "12 months" 这两个词组合而成的。
例句：
A year is made up of 12 months. (一年由12个月组成。)
Each year is divided into 12 months. (每年被划分成12个月。)
A year is a cycle of 12 months. (一年是12个月的循环。)