鲍克瑟的十二岁生日就在来年的夏末。

Boxer's twelfth birthday was due in the late summer of the following year.

这就是说她开始在霍格沃茨上学三个星期之后就过了十二岁生日，也就是说她比哈利和罗恩大了几乎一整岁。

That would mean that she turned twelve three weeks after starting Hogwarts and that she is almost a year older than Harry and Ron.