2 sentences for 不知 (bù​zhī — unknowingly)

1. 不知不觉中，天已经黑透了。

   bù​zhī bù jué zhōng, tiān yǐ​jīng hēi tòu le.

   Before I knew it, it had become pitch dark.

   Source: Dong Chinese Dictionary

2. 两人聊得投机，不知时间已过半夜。

   liǎng rén liáo de tóu​jī, bù​zhī shí​jiān yǐ guò bàn​yè.

   The two were having such a good conversation that they didn't realize it was already past midnight.

   Source: Dong Chinese Dictionary