diff --git a/gnu/local.mk b/gnu/local.mk
index 23af3f67d7..250c773992 100644
--- a/gnu/local.mk
+++ b/gnu/local.mk
@@ -972,6 +972,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/module-init-tools-moduledir.patch	\
   %D%/packages/patches/monero-use-system-miniupnpc.patch			\
   %D%/packages/patches/mongodb-support-unknown-linux-distributions.patch	\
+  %D%/packages/patches/mono-mdoc-timestamping.patch		\
   %D%/packages/patches/mozjs17-aarch64-support.patch		\
   %D%/packages/patches/mozjs24-aarch64-support.patch		\
   %D%/packages/patches/mozjs38-pkg-config-version.patch		\
diff --git a/gnu/packages/mono.scm b/gnu/packages/mono.scm
index 8ab449dd8e..17f90fe30a 100644
--- a/gnu/packages/mono.scm
+++ b/gnu/packages/mono.scm
@@ -41,7 +41,8 @@
                     ".tar.bz2"))
               (sha256
                (base32
-                "0jibyvyv2jy8dq5ij0j00iq3v74r0y90dcjc3dkspcfbnn37cphn"))))
+                "0jibyvyv2jy8dq5ij0j00iq3v74r0y90dcjc3dkspcfbnn37cphn"))
+              (patches (search-patches "mono-mdoc-timestamping.patch"))))
     (build-system gnu-build-system)
     (native-inputs
      `(("gettext" ,gettext-minimal)
@@ -52,10 +53,18 @@
     (arguments
      `(#:phases
        (modify-phases %standard-phases
+         (add-after 'unpack 'make-reproducible
+           (lambda _
+             (substitute* "mono/mini/Makefile.in"
+              (("build_date = [^;]*;")
+               "build_date = (void*) 0;"))
+             #t))
          (add-after 'unpack 'set-env
            (lambda _ ;;* (#:key inputs #:allow-other-keys)
              ;; all tests under mcs/class fail trying to access $HOME
              (setenv "HOME" "/tmp")
+             ;; ZIP files have "DOS time" which starts in Jan 1980.
+             (setenv "SOURCE_DATE_EPOCH" "315532800")
              #t))
          (add-after 'unpack 'fix-includes
            (lambda _
diff --git a/gnu/packages/patches/mono-mdoc-timestamping.patch b/gnu/packages/patches/mono-mdoc-timestamping.patch
new file mode 100644
index 0000000000..d5191a93eb
--- /dev/null
+++ b/gnu/packages/patches/mono-mdoc-timestamping.patch
@@ -0,0 +1,15 @@
+--- mono-4.4.1/mcs/class/monodoc/Monodoc/storage/ZipStorage.cs.orig	2018-11-26 22:16:25.008879747 +0100
++++ mono-4.4.1/mcs/class/monodoc/Monodoc/storage/ZipStorage.cs	2018-11-26 22:21:53.969770985 +0100
+@@ -74,6 +74,12 @@
+ 				id = GetNewCode ();
+ 
+ 			ZipEntry entry = new ZipEntry (id);
++			var SOURCE_DATE_EPOCH_string = Environment.GetEnvironmentVariable("SOURCE_DATE_EPOCH");
++			if (SOURCE_DATE_EPOCH_string != null)
++			{
++				var SOURCE_DATE_EPOCH = Convert.ToInt64(SOURCE_DATE_EPOCH_string);
++				entry.DateTime = new DateTime(SOURCE_DATE_EPOCH, DateTimeKind.Utc);
++			}
+ 			zipOutput.PutNextEntry (entry);
+ 		}
+