一個月有28日至31日，“一個月的星期日”就意味著連續三十個星期。另一種解釋是：一星期有七天，“一個月的星期日”可能意味著四個星期。總之，這個成語喻指“很長的時間”。例：He could easily have revenged himself by giving me a kick with heavy shoes on the head or the loins that would have spoiled my running for a month of Sundays.（他若要報仇，那很容易，只要用其沉重的靴尖向我頭部或腰部一踢，就可使我長時間不能行走。）

A: How about this work? 這個工作怎樣？
B: I think it will take me a month of Sundays to finish. 我想得花很長時間才能完成它。
A: You will have a long time to be very busy, right? 你又會忙一段時間了，是嗎？
B: Yeah. To be very tired, too. 就是，也會很累。
A: In some way, it is good for us because we can learn lots of things from it. 在某種程度上，這對我們有好處，因為我們能從中學到很多東西。

來源:可可英語 http://www.ccdyzl.cn/kouyu/201003/99319.shtml