diff --git a/pkgs/by-name/si/signal-desktop/package.nix b/pkgs/by-name/si/signal-desktop/package.nix
index 7ce2c0872db6..d07c3b5b51f6 100644
--- a/pkgs/by-name/si/signal-desktop/package.nix
+++ b/pkgs/by-name/si/signal-desktop/package.nix
@@ -60,10 +60,7 @@ let
     owner = "signalapp";
     repo = "Signal-Desktop";
     tag = "v${version}";
-    hash = "sha256-c76Z+AJCGBXpHPejtZaA2RJpEMy+sd2xvjx+epC1Eqw=";
-    postCheckout = ''
-      git -C "$out" show -s --format=%ct > "$out"/GIT_COMMIT_TIME
-    '';
+    hash = "sha256-Ay4mMurnEDNoFkEhxPn4SWBhrkNg94+AGFMrNA0mTcE=";
   };
 
   sticker-creator = stdenv.mkDerivation (finalAttrs: {
@@ -155,12 +152,9 @@ stdenv.mkDerivation (finalAttrs: {
   env = {
     ELECTRON_SKIP_BINARY_DOWNLOAD = "1";
     SIGNAL_ENV = "production";
+    SOURCE_DATE_EPOCH = 1767827358;
   };
 
-  preConfigure = ''
-    export SOURCE_DATE_EPOCH=`cat GIT_COMMIT_TIME`
-  '';
-
   preBuild = ''
     if [ "`jq -r '.engines.node' < package.json | cut -d. -f1`" != "${lib.versions.major nodejs.version}" ]
     then
diff --git a/pkgs/by-name/si/signal-desktop/update.sh b/pkgs/by-name/si/signal-desktop/update.sh
index a39078678c1d..d4dca6e74ef8 100755
--- a/pkgs/by-name/si/signal-desktop/update.sh
+++ b/pkgs/by-name/si/signal-desktop/update.sh
@@ -13,6 +13,8 @@ releaseInfo="`curl_github \
   "https://api.github.com/repos/signalapp/Signal-Desktop/releases/latest"`"
 
 releaseTag="`jq -r ".tag_name" <<< $releaseInfo`"
+releaseDate="`jq -r ".created_at" <<< $releaseInfo`"
+releaseEpoch=`date -d $releaseDate +%s`
 
 packageJson="`curl_github "https://raw.githubusercontent.com/signalapp/Signal-Desktop/refs/tags/$releaseTag/package.json"`"
 
@@ -27,6 +29,7 @@ webrtcVersion="`grep --only-matching "^webrtc.version=.*$" <<< $ringrtcVersionPr
 
 sed -E -i "s/(nodejs_)../\1$nodeVersion/" $SCRIPT_DIR/package.nix
 sed -E -i "s/(electron_)../\1$electronVersion/" $SCRIPT_DIR/package.nix
+sed -E -i "s/(SOURCE_DATE_EPOCH = )[0-9]+/\1$releaseEpoch/" $SCRIPT_DIR/package.nix
 
 sed -E -i "s/(withAppleEmojis \? )false/\1true/" $SCRIPT_DIR/package.nix
 nix-update signal-desktop --subpackage sticker-creator --version="$latestVersion"