Index: stamper/stamper.py
===================================================================
--- stamper/stamper.py	(revision 74)
+++ stamper/stamper.py	(revision 75)
@@ -11,4 +11,13 @@
 from .config import Config
 from .filters import DateFilter
+
+
+def timedelta_to_hms(value):
+    """
+    Return hours, minutes, seconds from a timedelta object
+    """
+    hours, remainder = divmod(int(value.total_seconds()), 3600)
+    minutes, seconds = divmod(remainder, 60)
+    return hours, minutes, seconds
 
 
@@ -299,4 +308,7 @@
             seconds=totals.get(customer, 0)
             total = timedelta(seconds=totals.get(customer, 0))
+            h, m, s = timedelta_to_hms(total)
+            total = ':'.join(
+                [str(h).zfill(2), str(m).zfill(2), str(s).zfill(2)])
             if not self.wants_seconds or self.wants_seconds == 'false':
                 # remove the seconds part from the string representation
@@ -308,4 +320,7 @@
                 seconds=totals[c]
                 total = timedelta(seconds=totals[c])
+                h, m, s = timedelta_to_hms(total)
+                total = ':'.join(
+                    [str(h).zfill(2), str(m).zfill(2), str(s).zfill(2)])
                 if not self.wants_seconds or self.wants_seconds == 'false':
                     # remove the seconds part from the string representation