中秋诗词《水调歌头﹒明月几时有》
Zhōngqiū shīcí--“shuǐ diào gē tóu﹒ Míngyuè jǐshí yǒu
 

Mid-Autumn Festival Poetry 
《To the tune of 'Shuǐ diào gē tóu', When will the Moon be Clear and Bright? 》

(Thinking of You)

There are many ancient poets who wrote poetry about the Mid-Autumn Festival. "Shuidiao ge tou, mingyue jishi you" which was written by Su Shi from Song Dynasty is the most well-known.
 

明月几时有，把酒问青天。
Míngyuè jǐshí yǒu, bǎjiǔ wèn qīngtiān.

不知天上宫阙，今夕是何年。
Bùzhī tiānshàng gōngjué, jīnxī shì hé nián.

我欲乘风归去，又恐琼楼玉宇，高处不胜寒。
Wǒ yù chéng fēng guī qù, yòu kǒng qióng lóu yùyǔ, gāo chù bùshèng hán.

起舞弄清影，何似在人间。
Qǐ wǔ nòng qīng yǐng, hé shì zài rénjiān.

转朱阁，低绮户，照无眠。
Zhuǎn zhū gé, dī qǐ hù, zhào wú mián.

不应有恨，何事长向别时圆。
Bù yìng yǒu hèn, héshì zhǎng xiàng bié shí yuán.

人有悲欢离合，月有阴晴圆缺，此事古难全。
Rén yǒu bēihuānlíhé, yuè yǒu yīn qíng yuán quē, cǐ shì gǔ nán quán.

但愿人长久，千里共婵娟。
Dàn yuàn rén chángjiǔ, qiānlǐ gòng chánjuān.
 

Like all poems, which are very difficult to translate into another language, this one is no exception. Wikipedia's translated version is below:

THINKING OF YOU

Mid-autumn of the Bing Chen year

Having been drinking happily over night
I'm drunk
So I write this poem
Remembering my brother, Zi You

When will the moon be clear and bright?

With a cup of wine in my hand, I ask the blue sky.
In the heavens on this night,
I wonder what season it would be?

I'd like to ride the wind to fly home.

Yet I fear the crystal and jade mansions
are much too high and cold for me.
Dancing with my moonlit shadow,
It does not seem like the human world.

The moon rounds the red mansion,

Stoops to silk-pad doors,
Shines upon the sleepless,
Bearing no grudge,
Why does the moon tend to be full when people are apart?

People may have sorrow or joy, be near or far apart,

The moon may be dim or bright, wax or wane,
This imperfection has been going on since the beginning of time.
May we all be blessed with longevity,
Though thousand miles apart, we are still able to share the beauty of the moon together.

Chinese people often write the last part of the poem, "但愿人长久，千里共婵娟。" to their family and friends that are not with them at Mid-Autumn Festival. 

To all our students at Mandarin House, we wish you all a safe and happy Mid-Autumn Festival and for all our past students who are now back home or all over China and/or the world, we wish you 但愿人长久，千里共婵娟!

The Mandarin House Team