diff --git a/hgext3rd/obsshelve.py b/hgext3rd/obsshelve.py
--- a/hgext3rd/obsshelve.py
+++ b/hgext3rd/obsshelve.py
@@ -57,6 +57,14 @@
     rebase,
 )
 
+try:
+    # New in hg 4.6
+    from mercurial.utils import dateutil
+    _makedate = dateutil.makedate
+except ImportError:
+    # 4.5 and earlier
+    _makedate = util.makedate
+
 configtable = {}
 configitem = registrar.configitem(configtable)
 configitem('obsshelve', 'maxbackups', default=10)
@@ -580,7 +588,7 @@
             continue
         ui.write(' ' * (16 - len(sname)))
         used = 16
-        age = '(%s)' % templatefilters.age(util.makedate(mtime), abbrev=True)
+        age = '(%s)' % templatefilters.age(_makedate(mtime), abbrev=True)
         ui.write(age, label='shelve.age')
         ui.write(' ' * (12 - len(age)))
         used += 12
@@ -1140,4 +1148,3 @@
     order = extensions._order
     if 'shelve' in order:
         raise error.Abort("shelve must be disabled when obsshelve is enabled")
-