It is the first time +that...从句
在“It is/was/will be the first time+that...从句”结构中,当主句动词为is/will be时
that分句动词一律用现在完成时；引导词that可以省略.
例如：It is the first time I’ve been here.
Don’t forget,it’ll be the first time I’ve spoken in public.
当主句动词为was时,that从句动词通常用过去完成时.
例如：It was the first time she’d been at a summer school and she thoroughly enjoyed