diff -r 4de15c54e59f -r c6061cadb400 mercurial/mdiff.py
--- a/mercurial/mdiff.py	Thu Feb 08 23:27:24 2018 +0530
+++ b/mercurial/mdiff.py	Thu Feb 15 17:18:26 2018 +0100
@@ -19,6 +19,7 @@
     pycompat,
     util,
 )
+from .utils import dateutil
 
 _missing_newline_marker = "\\ No newline at end of file\n"
 
@@ -255,7 +256,7 @@
         aprefix = 'a/'
         bprefix = 'b/'
 
-    epoch = util.datestr((0, 0))
+    epoch = dateutil.datestr((0, 0))
 
     fn1 = util.pconvert(fn1)
     fn2 = util.pconvert(fn2)