diff --git a/gramps2/ChangeLog b/gramps2/ChangeLog
index 88dffc389..cbb1a1863 100644
--- a/gramps2/ChangeLog
+++ b/gramps2/ChangeLog
@@ -6,6 +6,8 @@
 	* src/dates/Date_de.py: Register for all variants of german; Add other
 	variants of month names for parser
 
+	* src/Date.py: Raise Exception.DateError on invalid arguments
+
 2005-05-12  Don Allingham  <don@gramps-project.org>
 	* src/GrampsBSDDB.py: force database sync on transaction commit
 
diff --git a/gramps2/src/Date.py b/gramps2/src/Date.py
index c2b09e636..ce2bf5cee 100644
--- a/gramps2/src/Date.py
+++ b/gramps2/src/Date.py
@@ -25,6 +25,7 @@
 __author__ = "Donald N. Allingham"
 __version__ = "$Revision$"
 
+from Errors import DateError
 from CalSdn import *
 
 #-------------------------------------------------------------------------
@@ -143,9 +144,9 @@ class Date:
         Comparison function. Allows the usage of equality tests.
         This allows you do run statements like 'date1 <= date2'
         """
-	if isinstance(other,Date):
+        if isinstance(other,Date):
             return cmp(self.sortval,other.sortval)
-	else:
+        else:
             return -1
 
     def is_equal(self,other):
@@ -233,6 +234,8 @@ class Date:
         """
         Sets the modifier for the date.
         """
+        if val not in (MOD_NONE,MOD_BEFORE,MOD_AFTER,MOD_ABOUT,MOD_RANGE,MOD_SPAN,MOD_TEXTONLY):
+            raise DateError("Invalid modifier")
         self.modifier = val
 
     def get_quality(self):
@@ -250,6 +253,8 @@ class Date:
         """
         Sets the quality selected for the date.
         """
+        if val not in (QUAL_NONE,QUAL_ESTIMATED,QUAL_CALCULATED):
+            raise DateError("Invalid quality")
         self.quality = val
     
     def get_calendar(self):
@@ -270,6 +275,8 @@ class Date:
         """
         Sets the calendar selected for the date.
         """
+        if val not in (CAL_GREGORIAN,CAL_JULIAN,CAL_HEBREW,CAL_FRENCH,CAL_PERSIAN,CAL_ISLAMIC):
+            raise DateError("Invalid calendar")
         self.calendar = val
 
     def get_start_date(self):
@@ -427,6 +434,18 @@ class Date:
 
         The sort value is recalculated.
         """
+        
+        if modifier in (MOD_NONE,MOD_BEFORE,MOD_AFTER,MOD_ABOUT) and len(value) < 4:
+            raise DateError("Invalid value. Should be: (DD,MM,YY,slash)")
+        if modifier in (MOD_RANGE,MOD_SPAN) and len(value) < 8:
+            raise DateError("Invalid value. Should be: (DD,MM,YY,slash1,DD,MM,YY,slash2)")
+        if modifier not in (MOD_NONE,MOD_BEFORE,MOD_AFTER,MOD_ABOUT,MOD_RANGE,MOD_SPAN,MOD_TEXTONLY):
+            raise DateError("Invalid modifier")
+        if quality not in (QUAL_NONE,QUAL_ESTIMATED,QUAL_CALCULATED):
+            raise DateError("Invalid quality")
+        if calendar not in (CAL_GREGORIAN,CAL_JULIAN,CAL_HEBREW,CAL_FRENCH,CAL_PERSIAN,CAL_ISLAMIC):
+            raise DateError("Invalid calendar")
+
         self.quality = quality
         self.modifier = modifier
         self.calendar = calendar