Add a is_undefined_date method to utils.date

src/calibre/utils/date.py

@@ -46,6 +46,14 @@ local_tz = _local_tz = SafeLocalTimeZone()
 
 UNDEFINED_DATE = datetime(101,1,1, tzinfo=utc_tz)
 
+def is_date_undefined(qt_or_dt):
+    d = qt_or_dt
+    if hasattr(d, 'toString'):
+        d = datetime(d.year(), d.month(), d.day(), tzinfo=utc_tz)
+    return d.year == UNDEFINED_DATE.year and \
+            d.month == UNDEFINED_DATE.month and \
+            d.day == UNDEFINED_DATE.day
+
 def parse_date(date_string, assume_utc=False, as_utc=True, default=None):
     '''
     Parse a date/time string into a timezone aware datetime object. The timezone