光陰矢の如し

[kouin-ya-no-gotoshi]

Literal translation:

Light and darkness are like arrows.

Meaning:

Time flies.

Supplementary info:

“光” implies the sun, while “陰” connotes the moon.

“光陰” means time, like “月日 [tsukihi]” and “歳月 [saigetsu].”