Index: lib/redmine/i18n.rb
===================================================================
--- lib/redmine/i18n.rb	(revision 21522)
+++ lib/redmine/i18n.rb	(working copy)
@@ -89,6 +89,10 @@
       if Setting.timespan_format == 'minutes'
         h = hours.floor
         m = ((hours - h) * 60).round
+        if m == 60
+          h += 1
+          m = 0
+        end
         "%d:%02d" % [ h, m ]
       else
         "%.2f" % hours.to_f