of + a（an）时间结构在英语里是经常遇见的用法，其含义有两个：原指不一定哪个时间；在那个时间经常；用作状语；一般用来表示经常性的动作或习惯；具体请结合实例研习：
He comes of an evening.
他经常晚上来。
We would often have a walk of an evening.
我们过去常在晚上散步。
She always likes to go swimming of an evening.
她总喜欢晚上去游泳。
I like to relax with a pipe of a morning.
我喜欢于早晨用笛子来放松心情。
Sometimes he goes fishing of a morning.=
Sometimes he goes fishing habitually in the morning.
有时候他上午去钓鱼。
What do you do of a Sunday?=
What do you do on Sunday?
礼拜天你经常做什么？
I always go to church of a Sunday evening.
我总是在礼拜天的晚上去教堂做礼拜。
What time do they get up of a morning? 他们早晨几点钟起床?
He is a watchman and sleeps of a morning. 他是夜间警卫，所以上午常睡觉。
The memories came flooding back of a night in Belleville.
在贝尔维尔的夜晚往事常常涌上心头。