Avoid COM dates that end up with ms=1000, instead rounding to the nex…

…t second. Fixes #1655. (#1683)

CHANGES.txt

@@ -11,6 +11,10 @@ Since build 300:
 * Fix a bug in `win32profile.GetEnvironmentStrings()` relating to environment
   variables with an equals sign (@maxim-krikun in #1661)
 
+* Fixed a bug where certain COM dates would fail to be converted to a Python
+  datetime object with `ValueError: microsecond must be in 0..999999`. Shoutout
+  to @hujiaxing for reporting and helping reproduce the issue (#1655)
+
 * Added win32com.shell.SHGetKnownFolderPath() and related constants.
 
 * Shifted work in win32.lib.pywin32_bootstrap to Python's import system from

com/win32com/test/testPyComTest.py

@@ -273,6 +273,10 @@ def TestCommon(o, is_generated):
     later = now + datetime.timedelta(seconds=1)
     TestApplyResult(o.EarliestDate, (now, later), now)
 
+    # The below used to fail with `ValueError: microsecond must be in 0..999999` - see #1655
+    # https://planetcalc.com/7027/ says that float is: Sun, 25 Mar 1951 7:23:49 am
+    assert o.MakeDate(18712.308206013888) == datetime.datetime.fromisoformat("1951-03-25 07:23:49+00:00")
+
     progress("Checking currency")
     # currency.
     pythoncom.__future_currency__ = 1

win32/src/PyTime.cpp

@@ -380,11 +380,16 @@ PyObject *PyWin_NewTime(PyObject *timeOb)
         double minutes = (hours - (int)hours) * 60.0;
         double seconds = round((minutes - (int)minutes) * 60.0, 4);
         double milliseconds = round((seconds - (int)seconds) * 1000.0, 0);
-        // assert(milliseconds>=0.0 && milliseconds<=999.0);
-
         // Strip off the msec part of time
         double TimeWithoutMsecs = t - (ONETHOUSANDMILLISECONDS / 1000.0 * milliseconds);
 
+        // We might have rounded ms to 1000 which blows up datetime. Round up
+        // to the next second.
+        if (milliseconds >= 1000) {
+            TimeWithoutMsecs += ONETHOUSANDMILLISECONDS;
+            milliseconds = 0;
+        }
+
         // Let the OS translate the variant date/time
         SYSTEMTIME st;
         if (!VariantTimeToSystemTime(TimeWithoutMsecs, &st)) {