Index: stamper/filters.py
===================================================================
--- stamper/filters.py	(revision 65)
+++ stamper/filters.py	(revision 66)
@@ -68,41 +68,47 @@
         return self.months(current_date, months, '+')
 
-    def parse_number_filter(self, number_filter, future=False):
+    def parse_number_filter(self, number_filter, start_date=None,
+                            future=False):
         """
-        If a filter contains a number of days/months/years, try to find
-        out which filter it is exactly to apply it, then calculate the
-        number of days and find
+        Given a numeric filter with the N[d|w|m|y] pattern, return both
+        the number of days/months/years that apply as a filter, + the
+        date N[d|w|m|y] ago from start_date (which defaults to today if
+        None is passed).
+
+        If future is True, it will return a date in the future, not from
+        the past.
         """
         number = None
         filtered_date = None
+        start_date = start_date or datetime.today()
+
+        # set which methods use to process the date, going backwards into the
+        # past as a default, unless we are told otherwise
+        filter_days = self.days_ago
+        filter_months = self.months_ago
+        if future:
+            filter_days = self.days_future
+            filter_months = self.months_future
 
         if re.search(r'(\d+[dD]{1})', number_filter):
             number = int(number_filter.lower().replace('d', ''))
-            if future:
-                filtered_date = self.days_future(datetime.today(), number)
-            else:
-                filtered_date = self.days_ago(datetime.today(), number)
+            filtered_date = filter_days(start_date, number)
 
         elif re.search(r'(\d+[wW]{1})', number_filter):
             number = int(number_filter.lower().replace('w', '')) * 7
-            if future:
-                filtered_date = self.days_future(datetime.today(), number)
-            else:
-                filtered_date = self.days_ago(datetime.today(), number)
+            filtered_date = filter_days(start_date, number)
 
         elif re.search(r'(\d+[mM]{1})', number_filter):
             number = int(number_filter.lower().replace('m', ''))
-            if future:
-                filtered_date = self.months_future(datetime.today(), number)
-            else:
-                filtered_date = self.months_ago(datetime.today(), number)
+            filtered_date = filter_months(start_date, number)
 
         elif re.search(r'(\d+[yY]{1})', number_filter):
             number = int(number_filter.lower().replace('y', ''))
             today = date.today()
+            # by default assume going backwards into the past...
+            year = today.year - number
             if future:
+                #...unless told otherwise
                 year = today.year + number
-            else:
-                year = today.year - number
             filtered_date = datetime(year, today.month, today.day)
 
@@ -151,10 +157,20 @@
         elif '+' in stamp_filter:
             # "+" filtering works with a date following by "+", a number and
-            # a letter (d|w|m|y) which sets the number of days, months, years
-            # we would like to go into the future
-            filter_to, number = stamp_filter.split('+')
+            # a letter (d|w|m|y) which sets the number of days, weeks, months,
+            # years we would like to go into the future
+            filter_from, number = stamp_filter.split('+')
+            filter_from = datetime.strptime(filter_from, self.date_format)
+            number, filter_to = self.parse_number_filter(
+                number, filter_from, future=True)
+
+        elif stamp_filter.count('-') == 3:
+            # "-" filtering works with a date followed by "-", a number and
+            # a letter (d|w|m|y) which sets the number of days, weeks, months,
+            # years we would like to go backwards into the past
+            year, month, day, number = stamp_filter.split('-')
+            filter_to = '-'.join([year, month, day])
             filter_to = datetime.strptime(filter_to, self.date_format)
-            number, filter_from = self.parse_number_filter(number)
-            filter_from = self.days_ago(filter_to, int(number))
+            number, filter_from = self.parse_number_filter(number, filter_to)
+
         else:
             # Check if the user is asking for N days/weeks/months/years