I have the same problem as tangmonster911 and found this note in TimeLib.h.
// This ugly hack allows us to define C++ overloaded functions, when included
// from within an extern “C”, as newlib’s sys/stat.h does. Actually it is
// intended to include “time.h” from the C library (on ARM, but AVR does not
// have that file at all). On Mac and Windows, the compiler will find this
// “Time.h” instead of the C library “time.h”, so we may cause other weird
// and unpredictable effects by conflicting with the C library header “time.h”,
// but at least this hack lets us define C++ functions as intended. Hopefully
// nothing too terrible will result from overriding the C library header?!
Still trying to figure out how to fix it. I just upgraded to Arduino IDE 1.8.5 and am trying to compile OS 2.1.7. I have working versions of 2.1.6 on older Arduino IDE. I am wondering if this is a IDE issue or an issue the implementation of the override. I do not see this in 2.1.6
It would be good to hear from the people/person that wrote the note above.