都有可能.
区别的关键在于time放入定语从句中,是做句子的时间状语还是主语/宾语等名词性成分.
1. 如果定语从句缺少时间状语,一般用when
如：There was a time when the song was popular.
a time在从句中做时间状语
2. 如果定语从句缺少主语/宾语等名词性成分,则一般用which/that,有时还可以省略.
如：I‘ll never forget the time (which/that) I spent with you.
the time在从句中充当spent的宾语
另：下列句型中固定用that
This/It + is/was + the first/second... time +that从句
It be (high/about) time that从句