定语从句修饰时间名词表示将来，从句可用一般现在时代替将来时（传统语法观点）。

It is/was the first time that从句 用完成体。

It will be the first time that从句用一般体为非正式语体，用完成体为正式语体。

It will be the first time that she's given a professional speech on this trip. 

It will be the first time Trump addresses Congress.

Many experts said that the meeting is significant because it will be the first time the men will have spent so much time together.

It will be the first time I've been out of the country.

it will be the first time I've ever helped someone else find the perfect gift! 

It will be the first time in eight years that everyone is together.

If economists are right, it will be the first time that's ever happened.

It will be the first time that happens without the help of astronauts or Miles or human controllers.

It will be the first time Larry Kramer writes for the Southern Partisan.