Kakemono Japanese Calligraphy

calligraphy in ink, executed with a brush.
少年昜老學難成,一寸光陰不可輕.未覺池塘春草夢，階前梧葉已秋聲 .
the translation is: The young man is old, but he can't learn, and an inch of time is not something to be taken lightly. I haven't yet dreamed of spring grass in the pond, but the leaves in front of the stage have already sounded autumn.
This poem is about time passing too quickly, and that learning takes time. If you stray from this learning in your youth, you'll grow old without having completed it.
It was written by Zhu Xi (September 15, 1130 - April 23, 1200), a famous rationalist, thinker, philosopher, educator, poet and representative of the Min school of thought of the Southern Song dynasty, known as Zhu Zi, the most outstanding master of Confucianism since Confucius and Mencius.