说法以下几种：
There was a time when
eg：There was a time when I felt lonly.有段时间我感到很孤独
at one time
eg：The song had a great vogue at one time .这个歌曾经风行一时。
there once was a time
eg：Once upon a time, there were two men, who were brothers.从前有两个人，他们是兄弟。
for a while
eg：Now that I am free, I can enjoy music for a while.既然有空，我可以享受一下音乐
After a while.
eg：After dinner sit a while ; after supper walk a mile.谚饭后百步，延年益寿。