How to make a pointer point to a constant string in RAM

I'm using Keil3 for arm.
1\I wanna change the string's content,eg from "2007" to "2008"
2\I wanna a pointer ,not a array,to point to the string.
But when I do as follows:
char *ptr = "2007";
ptr is in the flash area,so I cann't change the content of the string "2007" .

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