WRONG:Write the report until 5 pm.
RIGHT: Write the report by 5 pm.
Write the report until 5 pm means “Start writing the report now, continue writing it until 5 pm, then stop writing it regardless of whether it is finished or not.”
当你使用“until”意味着“从现在开始写报告，一直写，写到下午五点，然后不管你写没写完，都不能再写了”。
Write the report by 5 pm means “Make sure that at 5 pm the letter is written and finished”.
当你使用“by”就表示“确保一定要在下午五点前写完这封信”。
Use “by” when you refer to a deadline.
使用“by”，你指的是一个最后期限。
Use “until” when you refer to the period of time before a deadline.
使用“until”，你指的是在最后期限之前的一段时间。
Here’s a summary:
总结：
1.I can do it by 5 pm.
我能在下午五点前做完。
2.I can do it until 5 pm.
我会做到下午五点(不管有没有完成)。
3.I can’t do it by 5 pm.
下午五点前我做不完。
4.I can’t do it until 5 pm.
我要到下午五点才能开始做。
