Index: stamper/stamper.py
===================================================================
--- stamper/stamper.py	(revision 24)
+++ stamper/stamper.py	(revision 25)
@@ -9,5 +9,6 @@
 
 STAMPS_FILE = expanduser('~/.workstamps.json')
-DATE_FORMAT = '%Y-%m-%d %H:%M'
+DATE_FORMAT = '%Y-%m-%d'
+DATETIME_FORMAT = '%Y-%m-%d %H:%M'
 HOURS_DAY = 8
 SECS_DAY = HOURS_DAY * 60 * 60
@@ -51,6 +52,6 @@
 
     def worktime(self, start, end):
-        worktime = (datetime.strptime(end, DATE_FORMAT) -
-                    datetime.strptime(start, DATE_FORMAT))
+        worktime = (datetime.strptime(end, DATETIME_FORMAT) -
+                    datetime.strptime(start, DATETIME_FORMAT))
         return worktime.seconds