verb, often, used in the negative
to return; to come back
你聰明的，告訴我，我們的日子為什麼一去不復返呢？
你聪明的，告诉我，我们的日子为什么一去不复返呢？
nǐ cōng míng de ， gào su wǒ ， wǒ men de rì zi wèi shén me yī qù bù fù fǎn ne ？ You the wise, tell me, why should our days leave us, never to return?
The days we light candles on the corridor with neighbors at Mid-Autumn festival was gone and never be back.
Examples (Wiktionary)
Mandarin
你聪明的，告诉我，我们的日子为什么一去不复返呢？
你聰明的，告訴我，我們的日子為什麼一去不復返呢？
nǐ cōng míng de ， gào su wǒ ， wǒ men de rì zi wèi shén me yī qù bù fù fǎn ne ？
You the wise, tell me, why should our days leave us, never to return?
Mandarin
现在，她就要走了，就在走的一刻，米籽心里却有点起毛，因为此刻的心情与她原先想像的有一点不同，她原以为憧憬了三年的流浪生涯一日迈步便将如“壮士一去不复返”般的慷慨，可真的将梦想兑换成现实的最后关头，却发现自己仍在作种种挣扎。
現在，她就要走了，就在走的一刻，米籽心裏卻有點起毛，因為此刻的心情與她原先想像的有一點不同，她原以為憧憬了三年的流浪生涯一日邁步便將如“壯士一去不復返”般的慷慨，可真的將夢想兑換成現實的最後關頭，卻發現自己仍在作種種掙扎。
xiàn zài ， tā jiù yào zǒu le ， jiù zài zǒu de yī kè ， mǐ zǐ xīn lǐ què yǒu diǎn qǐ máo ， yīn wèi cǐ kè de xīn qíng yǔ tā yuán xiān xiǎng xiàng de yǒu yī diǎn bù tóng ， tā yuán yǐ wèi chōng jǐng le sān nián de liú làng shēng yá yī rì mài bù biàn jiāng rú “ zhuàng shì yī qù bù fù fǎn ” bān de kāng kǎi ， kě zhēn de jiāng mèng xiǎng duì huàn chéng xiàn shí de zuì hòu guān tóu ， què fā xiàn zì jǐ réng zài zuò zhǒng zhǒng zhèng zhá ．
Now, she was about to leave. Right at the moment when she was leaving, Mizi got a little flustered in her heart because how she felt at this moment was different from how she originally imagined it. She had thought that once she stepped into the vagrant life she had been longing for for three years, she would have a big heart as "a warrior that goes without returning", but at the last critical point before her dream is exchanged for reality, she realized that she was still dealing with all sorts of struggles.
Mandarin
人民所厌恶的国家分裂和混乱的局面，已经一去不复返了。
人民所厭惡的國家分裂和混亂的局面，已經一去不復返了。
rén mín suǒ yà nè de guó jiā fēn liè hé hùn luàn de jú miàn ， yǐ jīng yī qù bù fù fǎn le ．
The days of national disunity and chaos which the people detested are gone, never to return.