diff --git a/development/build/etc.js b/development/build/etc.js
index a75cd650f..3da86409f 100644
--- a/development/build/etc.js
+++ b/development/build/etc.js
@@ -49,7 +49,10 @@ function createZipTask(platform, buildType, version) {
       gulp.src(`dist/${platform}/**`),
       // sort files and set `mtime` to epoch to ensure zip build is deterministic
       sort(),
-      gulpZip(`${path}.zip`, { modifiedTime: new Date(0) }),
+      // Modified time set to an arbitrary static date to ensure build the is reproducible.
+      // The date chosen is MetaMask's birthday. Originally we chose the Unix epoch, but this
+      // resulted in invalid dates on certain timezones/operating systems.
+      gulpZip(`${path}.zip`, { modifiedTime: new Date('2016-07-14T00:00:00') }),
       gulp.dest('builds'),
     );
   };