Examples
zhè这gè个yuè dǐ月底qián前，wǒ men我们bì xū必须jiāo交bào gào报告。
这个月底前，我们必须交报告。
We have to turn in our reports by the end of this month.
四月底，黄河的水发黑了。
At the end of April, the water of the Yellow River had darkened.
请在四月底之前交上你的学期报告。
You should turn in your term papers by the end of April.