+#ifdef __MACH__
+
+       #define CLOCK_MONOTONIC (1)
+       #define CLOCK_REALTIME (2)
+
+       #include <sys/time.h>
+       #include <mach/clock.h>
+       #include <mach/mach.h>
+       #include <mach/mach_time.h>
+
+       /* clock_gettime is not implemented on OSX prior to 10.12 */
+       int _civet_clock_gettime(int clk_id, struct timespec *t);
+
+       int _civet_clock_gettime(int clk_id, struct timespec *t)
+       {
+               memset(t, 0, sizeof(*t));
+               if (clk_id == CLOCK_REALTIME) {
+                       struct timeval now;
+                       int rv = gettimeofday(&now, NULL);
+                       if (rv) {
+                               return rv;
+                       }
+                       t->tv_sec = now.tv_sec;
+                       t->tv_nsec = now.tv_usec * 1000;
+                       return 0;
+
+               } else if (clk_id == CLOCK_MONOTONIC) {
+                       static uint64_t clock_start_time = 0;
+                       static mach_timebase_info_data_t timebase_ifo = {0, 0};
+
+                       uint64_t now = mach_absolute_time();
+
+                       if (clock_start_time == 0) {
+                               //kern_return_t mach_status = mach_timebase_info(&timebase_ifo);
+                               // appease "unused variable" warning for release builds
+                               //(void)mach_status;
+                               clock_start_time = now;
+                       }
+
+                       now = (uint64_t)((double)(now - clock_start_time)
+                                        * (double)timebase_ifo.numer
+                                        / (double)timebase_ifo.denom);
+
+                       t->tv_sec = now / 1000000000;
+                       t->tv_nsec = now % 1000000000;
+                       return 0;
+               }
+               return -1; // EINVAL - Clock ID is unknown
+       }
+
+       /* if clock_gettime is declared, then __CLOCK_AVAILABILITY will be defined */
+       #ifdef __CLOCK_AVAILABILITY
+               /* If we compiled with Mac OSX 10.12 or later, then clock_gettime will be declared
+                * but it may be NULL at runtime. So we need to check before using it. */
+               int _civet_safe_clock_gettime(int clk_id, struct timespec *t);
+
+               int _civet_safe_clock_gettime(int clk_id, struct timespec *t) {
+                       if( clock_gettime ) {
+                               return clock_gettime(clk_id, t);
+                       }
+                       return _civet_clock_gettime(clk_id, t);
+               }
+               #define clock_gettime _civet_safe_clock_gettime
+       #else
+               #define clock_gettime _civet_clock_gettime
+       #endif
+
+#endif
+
+