uv_hrtime() always uses a monotonic clock but that is not sufficient for all applications.

Example: new Date() in node.js currently needs platform-specific code because the spec mandates the use of a real-time clock (i.e., human time.)

My proposal:

struct uv_timespec {
  int64_t sec;  /* Seconds since UNIX epoch.  Negative for dates < 1970. */
  uint32_t nsec;
};

enum uv_clock_id {
  UV_CLOCK_MONOTONIC,
  UV_CLOCK_MONOTONIC_COARSE,  // XXX define as "at least 1 ms precision"?
  UV_CLOCK_REALTIME,
  UV_CLOCK_REALTIME_COARSE
 };

int uv_clock_gettime(enum uv_clock_id id, struct uv_timespec* ts);

Look familiar? uv_hrtime() can be reimplemented in terms of uv_clock_gettime().

Other interesting clocks can be added later if we error with UV_EINVAL for invalid clock ids so that downstream users can detect their (lack of) support at run-time.

The Windows implementation would probably use GetSystemTimePreciseAsFileTime() or GetSystemTimeAsFileTime() for the real-time clock.

Like gettimeofday() and clock_gettime(CLOCK_REALTIME), they return the time in UTC, but in "100-nanosecond intervals since January 1, 1601 (UTC)" according to MSDN.