The meaning of this poem is: reading at night while burning the midnight oil, crowing at night, this morning and night are the best time for boys to study. When I was a teenager, I only knew how to play and didn't know how to study hard. When I was old, I regretted why I didn't know how to study hard when I was young.
The purpose of this poem is to encourage young people to cherish their youth, study hard and make a difference, otherwise it will be too late to regret.
The source of this poem is: Yan Zhenqing's poem.
The author of this poem is: Yan Zhenqing (709-784), a famous official and calligrapher in the Tang Dynasty, who is also called "four masters of regular script" with Zhao Mengfu, Liu Gongquan and Ou Yangxun.