is there a time 后面多跟when引导的从句,它的意思多有以下2种：
1.是否曾经……过?
例如,Is there a time when you felt upset and even wanted to give up?
你是否曾经沮丧甚至一度想要放弃?
2.是不是有那么一段时间……?
Is there a time of the year when I am most likely to get the flu?
一年中,是不是有那么一段时间我特别容易得感冒?