一年有多少天用英语说是 "how many days in a year"。这个短语来源于英语中最基本的问题结构，即“how + adj/adv + subject + verb”。
例句1: "How many days are there in a year?" (一年有多少天？)
例句2: "I always forget how many days are in a year." (我总是忘记一年有多少天。)
例句3: "Can you tell me how many days there are in a year?" (你能告诉我一年有多少天吗？)