diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,9 @@
 
 ## WIP
 
+## [0.2.8] - 2021-07-19
+- Add `unstable-` prefix to versions when using dates
+
 ## [0.2.7] - 2021-05-23
 
 - `hnix-0.13` support
diff --git a/default.nix b/default.nix
--- a/default.nix
+++ b/default.nix
@@ -10,15 +10,7 @@
 in hp.developPackage {
   name = "update-nix-fetchgit";
   root = nix-gitignore.gitignoreSource [ ] ./.;
-  overrides = self: super: {
-    hnix = pkgs.haskell.lib.dontCheck (self.callHackageDirect {
-      pkg = "hnix";
-      ver = "0.13.1";
-      sha256 = "0v3r33azlv050fv8y5vw0pahdnch7vqq94viwrp9vlw8hpiys8qn";
-    } { });
-    relude = self.relude_1_0_0_1;
-    semialign = self.semialign_1_2;
-  };
+  overrides = self: super: { };
   modifier = drv: haskell.lib.addBuildTools drv [ git nix nix-prefetch-git ];
   returnShellEnv = forShell;
 }
diff --git a/package.yaml b/package.yaml
--- a/package.yaml
+++ b/package.yaml
@@ -1,5 +1,5 @@
 name: update-nix-fetchgit
-version: "0.2.7"
+version: "0.2.8"
 synopsis: A program to update fetchgit values in Nix expressions
 description: |
   This command-line utility is meant to be used by people maintaining Nix
diff --git a/src/Update/Nix/FetchGit.hs b/src/Update/Nix/FetchGit.hs
--- a/src/Update/Nix/FetchGit.hs
+++ b/src/Update/Nix/FetchGit.hs
@@ -135,11 +135,12 @@
       let latestDate = maximumMay (catMaybes ds)
       pure
         ( latestDate
-        , [ SpanUpdate (exprSpan v) (quoteString . pack . show $ d)
+        , [ SpanUpdate (exprSpan v)
+                       (quoteString . ("unstable-" <>) . pack . show $ d)
           | Just d <- pure latestDate
           , Just v <- pure versionExpr
           ]
-          <> concat ss
+        <> concat ss
         )
 
 ----------------------------------------------------------------
diff --git a/src/Update/Nix/FetchGit/Utils.hs b/src/Update/Nix/FetchGit/Utils.hs
--- a/src/Update/Nix/FetchGit/Utils.hs
+++ b/src/Update/Nix/FetchGit/Utils.hs
@@ -38,8 +38,7 @@
                                                 )
 import           Nix.Atoms                      ( NAtom(NBool) )
 import           Nix.Expr                hiding ( SourcePos )
-import           Nix.Parser                     ( Result
-                                                , parseNixFileLoc
+import           Nix.Parser                     ( parseNixFileLoc
                                                 , parseNixTextLoc
                                                 )
 import           Update.Nix.FetchGit.Types
@@ -92,7 +91,6 @@
 -- | Get the 'SrcSpan' covering a particular expression.
 exprSpan :: NExprLoc -> SrcSpan
 exprSpan (AnnE s _) = s
-exprSpan _ = error "unreachable" -- TODO: Add pattern completeness to hnix
 
 -- | Given an expression that is supposed to represent a function,
 -- extracts the name of the function.  If we cannot figure out the
diff --git a/tests/fakeRepo.sh b/tests/fakeRepo.sh
--- a/tests/fakeRepo.sh
+++ b/tests/fakeRepo.sh
@@ -12,6 +12,8 @@
 export GIT_AUTHOR_NAME='joe'
 export GIT_COMMITTER_EMAIL='joe@example.com'
 export GIT_AUTHOR_EMAIL='joe@example.com'
+export XDG_CONFIG_DIRS=
+export HOME=
 
 git init repo1
 cd repo1
diff --git a/tests/networked/test_readme_examples.expected.nix b/tests/networked/test_readme_examples.expected.nix
--- a/tests/networked/test_readme_examples.expected.nix
+++ b/tests/networked/test_readme_examples.expected.nix
@@ -2,7 +2,7 @@
   a = { stdenv, fetchgit }:
     stdenv.mkDerivation rec {
       name = "foo-${version}";
-      version = "2016-06-26";
+      version = "unstable-2016-06-26";
       # ^ version will be updated to the date of the new revision
       src = fetchgit {
         url = "/tmp/nix-update-fetchgit-test/repo1";
diff --git a/tests/test_max_version.expected.nix b/tests/test_max_version.expected.nix
--- a/tests/test_max_version.expected.nix
+++ b/tests/test_max_version.expected.nix
@@ -1,9 +1,9 @@
 {
-  version = "2016-07-08";
+  version = "unstable-2016-07-08";
   repos = {
-    version = "2016-07-08";
+    version = "unstable-2016-07-08";
     repo1 = {
-      version = "2016-06-26";
+      version = "unstable-2016-06-26";
       src = fetchgit {
         url = "/tmp/nix-update-fetchgit-test/repo1";
         rev = "1c60ae07b5740aab02e32b4f64600f002112e6fd";
@@ -11,7 +11,7 @@
       };
     };
     repo2 = {
-      version = "2016-07-08";
+      version = "unstable-2016-07-08";
       src = fetchgit {
         url = "/tmp/nix-update-fetchgit-test/repo2";
         rev = "1ac598e1fd0ec3556f1349bb5fd8d08d89580c8a";
diff --git a/tests/test_rec_sets.expected.nix b/tests/test_rec_sets.expected.nix
--- a/tests/test_rec_sets.expected.nix
+++ b/tests/test_rec_sets.expected.nix
@@ -1,6 +1,6 @@
 rec {
   name = "foobar-${version}";
-  version = "2016-06-26";
+  version = "unstable-2016-06-26";
   src = fetchgit rec {
     url = "/tmp/nix-update-fetchgit-test/repo1";
     rev = "1c60ae07b5740aab02e32b4f64600f002112e6fd";
diff --git a/tests/test_updates_with_other_errors.expected.nix b/tests/test_updates_with_other_errors.expected.nix
--- a/tests/test_updates_with_other_errors.expected.nix
+++ b/tests/test_updates_with_other_errors.expected.nix
@@ -1,5 +1,5 @@
 {
-  version = "2016-06-26";
+  version = "unstable-2016-06-26";
 
   should-error = fetchgit rec {
     url = "/tmp/nix-update-fetchgit-test/missingRepo";
diff --git a/tests/test_version_update.expected.nix b/tests/test_version_update.expected.nix
--- a/tests/test_version_update.expected.nix
+++ b/tests/test_version_update.expected.nix
@@ -1,5 +1,5 @@
 {
-  version = "2016-06-26";
+  version = "unstable-2016-06-26";
   src = fetchgit {
     url = "/tmp/nix-update-fetchgit-test/repo1";
     rev = "1c60ae07b5740aab02e32b4f64600f002112e6fd";
diff --git a/update-nix-fetchgit.cabal b/update-nix-fetchgit.cabal
--- a/update-nix-fetchgit.cabal
+++ b/update-nix-fetchgit.cabal
@@ -5,7 +5,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           update-nix-fetchgit
-version:        0.2.7
+version:        0.2.8
 synopsis:       A program to update fetchgit values in Nix expressions
 description:    This command-line utility is meant to be used by people maintaining Nix
                 expressions that fetch files from Git repositories. It automates the process