In the Spring and Autumn Period, a man in the state of Song raised monkeys.

The monkeys could understand what he said.

As the man became poor, he wanted to reduce the monkeys' food.

He first suggested that he give them three acorns(橡子) in the morning and four acorns in the evening.

Thereupon, the monkeys protested angrily.

Then their owner said, "How about four in the morning and three in the evening?

" The monkeys were satisfied with that.

This idiom originally meant to befool others with tricks.

Later it is used to mean to keep changing one's mind.

战国时代，宋国有一个养猴子的老人，他在家中的院子里养了许多猴子。

日子一久，这个老人和猴子竟然能沟通讲话了。

这个老人每天早晚都分别给每只猴子四颗栗子。

几年之后，老人的经济越来越不充裕了，而猴子的数目却越来越多，所以他就想把每天的栗子由八颗改为七颗，于是他就和猴子们商量说：从今天开始，我每天早上给你们三颗粟子，晚上还是照常给你们四颗栗子，不知道你们同不同意?

”猴子们听了，都认为早上怎么少了一个?

于是一个个就开始吱吱大叫，而且还到处跳来跳去，好像非常不愿意似的。

老人一看到这个情形，连忙改口说：那么我早上给你们四颗，晚上再给你们三颗，这样该可以了吧?

”猴子们听了，以为早上的粟子已经由三个变成四个，跟以前一样，就高兴地在地上翻滚起来。

【中国成语故事中英对照 朝三暮四查看网站：[db:时间]】