Something birds, something stones?

一朝一夕
i-.cchou.i-.sseki

Literally: one – morning – one – evening

Alternately: A single day. By extension, a brief and fleeting span of time. Often used in a negative structure to express that something can’t be done in (such) a small amount of time.

Notes: This compound comes to us from the I Ching (易経, in Japanese Ekikyou).

In a variant, the character 朝 is replaced with 旦 (tan), “daybreak.” Meanwhile, while 夕 can often be read as yuu, doing so in either variant of this compound is considered an error.

From this site, which tries to be cute by saying that the commonality between diets and asset management is that they both can’t be done in 一朝一夕.