David Ripton avatar David Ripton committed 235d8b8

Copy function utcfromtimestamp from CPython 3.2's datetime.py

Fixes issue972, which was caused by rounding differences between
fromtimestamp and utcfromtimestamp.

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Files changed (1)


         return result
     fromtimestamp = classmethod(fromtimestamp)
+    @classmethod
     def utcfromtimestamp(cls, t):
         "Construct a UTC datetime from a POSIX timestamp (like time.time())."
-        if 1 - (t % 1.0) < 0.0000005:
-            t = float(int(t)) + 1
-        if t < 0:
-            t -= 1
+        t, frac = divmod(t, 1.0)
+        us = round(frac * 1e6)
+        # If timestamp is less than one microsecond smaller than a
+        # full second, us can be rounded up to 1000000.  In this case,
+        # roll over to seconds, otherwise, ValueError is raised
+        # by the constructor.
+        if us == 1000000:
+            t += 1
+            us = 0
         y, m, d, hh, mm, ss, weekday, jday, dst = _time.gmtime(t)
-        us = int((t % 1.0) * 1000000)
         ss = min(ss, 59)    # clamp out leap seconds if the platform has them
         return cls(y, m, d, hh, mm, ss, us)
-    utcfromtimestamp = classmethod(utcfromtimestamp)
     # XXX This is supposed to do better than we *can* do by using time.time(),
     # XXX if the platform supports a more accurate way.  The C implementation
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