. the problem is if ı plugged Adafruit on arduino, there will be no open (extra) pin s for theRtc shield.
I guess it doesn't work the other way round either and your problem is that the shields are not stackable.
One solution is to make for yourself an RTC shield that is. This could be done with a proto shield kit and a Tiny RTC module and should cost less than $10. Only four connections are needed - 5v, gnd, SDA, and SCL.
On a Uno, the latter two go to pins A4,A5, so all you have to do is ensure that the motor shield does not use those. In the highly unlikely event that it does, you could switch from Uno to a Mega, which uses different pins for SDA, SCL and you can be quite sure the motor shield will not clash with them.