diff --git a/mercurial/templater.py b/mercurial/templater.py
--- a/mercurial/templater.py
+++ b/mercurial/templater.py
@@ -913,7 +913,7 @@
         tzoffset = None
         tz = evalfuncarg(context, mapping, args[1])
         if isinstance(tz, str):
-            tzoffset, remainder = util.parsetimezone(tz)
+            tzoffset, remainder = dateutil.parsetimezone(tz)
             if remainder:
                 tzoffset = None
         if tzoffset is None:
diff --git a/mercurial/util.py b/mercurial/util.py
--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -1906,34 +1906,6 @@
             limit -= len(s)
         yield s
 
-def parsetimezone(s):
-    """find a trailing timezone, if any, in string, and return a
-       (offset, remainder) pair"""
-
-    if s.endswith("GMT") or s.endswith("UTC"):
-        return 0, s[:-3].rstrip()
-
-    # Unix-style timezones [+-]hhmm
-    if len(s) >= 5 and s[-5] in "+-" and s[-4:].isdigit():
-        sign = (s[-5] == "+") and 1 or -1
-        hours = int(s[-4:-2])
-        minutes = int(s[-2:])
-        return -sign * (hours * 60 + minutes) * 60, s[:-5].rstrip()
-
-    # ISO8601 trailing Z
-    if s.endswith("Z") and s[-2:-1].isdigit():
-        return 0, s[:-1]
-
-    # ISO8601-style [+-]hh:mm
-    if (len(s) >= 6 and s[-6] in "+-" and s[-3] == ":" and
-        s[-5:-3].isdigit() and s[-2:].isdigit()):
-        sign = (s[-6] == "+") and 1 or -1
-        hours = int(s[-5:-3])
-        minutes = int(s[-2:])
-        return -sign * (hours * 60 + minutes) * 60, s[:-6]
-
-    return None, s
-
 def strdate(string, format, defaults=None):
     """parse a localized time string and return a (unixtime, offset) tuple.
     if the string cannot be parsed, ValueError is raised."""
@@ -1941,7 +1913,7 @@
         defaults = {}
 
     # NOTE: unixtime = localunixtime + offset
-    offset, date = parsetimezone(string)
+    offset, date = dateutil.parsetimezone(string)
 
     # add missing elements from defaults
     usenow = False # default to using biased defaults
@@ -3877,3 +3849,9 @@
     nouideprecwarn(msg, "4.6")
     return dateutil.shortdate(*args, **kwargs)
 
+def parsetimezone(*args, **kwargs):
+    msg = ("'util.parsetimezone' is deprecated, "
+           "use 'utils.dateutil.parsetimezone'")
+    nouideprecwarn(msg, "4.6")
+    return dateutil.parsetimezone(*args, **kwargs)
+
diff --git a/mercurial/utils/dateutil.py b/mercurial/utils/dateutil.py
--- a/mercurial/utils/dateutil.py
+++ b/mercurial/utils/dateutil.py
@@ -111,3 +111,31 @@
     """turn (timestamp, tzoff) tuple into iso 8631 date."""
     return datestr(date, format='%Y-%m-%d')
 
+def parsetimezone(s):
+    """find a trailing timezone, if any, in string, and return a
+       (offset, remainder) pair"""
+
+    if s.endswith("GMT") or s.endswith("UTC"):
+        return 0, s[:-3].rstrip()
+
+    # Unix-style timezones [+-]hhmm
+    if len(s) >= 5 and s[-5] in "+-" and s[-4:].isdigit():
+        sign = (s[-5] == "+") and 1 or -1
+        hours = int(s[-4:-2])
+        minutes = int(s[-2:])
+        return -sign * (hours * 60 + minutes) * 60, s[:-5].rstrip()
+
+    # ISO8601 trailing Z
+    if s.endswith("Z") and s[-2:-1].isdigit():
+        return 0, s[:-1]
+
+    # ISO8601-style [+-]hh:mm
+    if (len(s) >= 6 and s[-6] in "+-" and s[-3] == ":" and
+        s[-5:-3].isdigit() and s[-2:].isdigit()):
+        sign = (s[-6] == "+") and 1 or -1
+        hours = int(s[-5:-3])
+        minutes = int(s[-2:])
+        return -sign * (hours * 60 + minutes) * 60, s[:-6]
+
+    return None, s
+