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Supposing you are referring to the DS1307RTC by Paul Stoffregen, you could try the following (I don't have a DS1307, so I can't test it): 1. Open the library file DS1307RTC.cpp. 2. Search & replace all instances (67 or so, let your editor do this for you) of 'Wire' by 'MyWire' except for the very first at the top of the file, ie do not change the include: #include <Wire.h> 3. Save the file. 4. Add the following define in the sketch before the inclusion of the file DS1307RTC.h: #define MyWire Wire1 #include <Time.h> #include <TimeLib.h> #include <DS1307RTC.h> Without the define the library wil use I2C0 as before, with it, it will switch to I2C1 instead. 5. Compile the sketch. After these modifications the ReadTest example compiles without warnings & errors (it does for me). Final note: you are bound to forget that you modified a library, so it is better to rename the modified library to avoid strange errors in other sketches that rely on the same library.