last,next,this前什么情况下加the

next+以现在为标准的时间-即当谈到紧接着眼前这一周\这一月\这一年的下一周\下一月\下一年.
eg:I shall have been in thee army for fully three years by July next year.
the next+以过去或将来为标准的时间-即当谈到紧接过去或将来的某一周\某一月\某一年的下一周\下一月\下一年.
eg:The forign guests spend the first week in Beijing and the next week in Shanghai.
还有一点,
next+时间名词－前不可加任何介词
the next +时间名词－前可用适当介词（也可省略
last和next类似
而this 前不加the