It's time...后的定语从句通常用that引导。若 time 后跟 when 从句，则其前面多有其他词如 a / the 等。如：
1. It was a time when anything seemed possible. 那是一个任何事可能发生的时代。
2. It was a time when she could not bear the pain and wantedto kill herself. 她曾经无法忍受病痛，想结束自己的生命。
3. It was a time when you could discover a new poet, meet a lifelong friend, fallin love and completely alter your world view, all within a single term; andthen do it all again next term. 那些日子里你能够在一个学期里发现一位新的诗人，遇见一个终生好友，谈一场恋爱，重塑你的世界观，然后再在第二个学期中将上述的事情通通重复一遍。
4. Some scientists claim that spring is not March, nor April, nor May. Instead, they say it is the time when the nights aregetting shorter, the days longer. 一些科学家主张春天非是始于三月，四月，或者五月。他们认为当夜晚逐渐变短白天开始变长，就是春回大地之时。
5.It is the time at which / that / when relatives and friends exchangevisits. 那是走亲访友的时间。