Perhaps. But the library doesn't lock you in to a particular RTC library. It only requires that you include some RTC library and set that libraries 'now()' method as the time sync provider. It does however, depend on the DateTime library for that kind of usage.
So it should be very easy to modify solarTimeRTC to work with any RTC library, including the Rinky Dink Electronics one. You just need to use the correct functions that belong to that library. You are using functions that belong to a different library, that is the source of your errors.