what's wrong in your code. You have used the XBYTE macros to access the RTC. This is fine and it maps your RTC into XDATA space. Since P2.5 is the RTC !CS, all the addresses in your macros are valid with CS low. Whenever the macro is executed, the Chip is Selected irrespective of what you do with the rtcce sbit. Were you not to use the XBYTE macros, the rtcce sbit would matter. But, in that case, you would also need to manipulate the RD and WR signals.

I can suggest you write P2 = 0xFF at the start of your program and never touch it again. Just delete the line with rtcce = 0 etc since you don't need it. The macros will work fine and there will be no memory contention unless you have other devices that map onto the 8xxxH space.