diff --git a/toolkit/components/osfile/modules/osfile_unix_front.jsm b/toolkit/components/osfile/modules/osfile_unix_front.jsm
index 11ed684e964e..43ba86406ccc 100644
--- a/toolkit/components/osfile/modules/osfile_unix_front.jsm
+++ b/toolkit/components/osfile/modules/osfile_unix_front.jsm
@@ -1148,10 +1148,12 @@
       let timevals = new Type.timevals.implementation();
       let timevalsPtr = timevals.address();
 
+      // JavaScript date values are expressed in milliseconds since epoch.
+      // Split this up into second and microsecond components.
       timevals[0].tv_sec = (accessDate / 1000) | 0;
-      timevals[0].tv_usec = 0;
+      timevals[0].tv_usec = ((accessDate % 1000) * 1000) | 0;
       timevals[1].tv_sec = (modificationDate / 1000) | 0;
-      timevals[1].tv_usec = 0;
+      timevals[1].tv_usec = ((modificationDate % 1000) * 1000) | 0;
 
       return { value: timevals, ptr: timevalsPtr };
     }
diff --git a/toolkit/mozapps/extensions/internal/AddonTestUtils.jsm b/toolkit/mozapps/extensions/internal/AddonTestUtils.jsm
index b2958608efb6..d75ebef97b97 100644
--- a/toolkit/mozapps/extensions/internal/AddonTestUtils.jsm
+++ b/toolkit/mozapps/extensions/internal/AddonTestUtils.jsm
@@ -1443,7 +1443,7 @@ var AddonTestUtils = {
   },
 
   async promiseSetExtensionModifiedTime(path, time) {
-    await OS.File.setDates(path, time, time);
+    await IOUtils.touch(path, time);
 
     let iterator = new OS.File.DirectoryIterator(path);
     try {
diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_schema_change.js b/toolkit/mozapps/extensions/test/xpcshell/test_schema_change.js
index 60922cc7f045..85c1a03f41c0 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_schema_change.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_schema_change.js
@@ -79,12 +79,9 @@ add_task(async function run_tests() {
       what: "Modified timestamp on the XPI causes a reload of the manifest.",
       expectedVersion: "2.0",
       async action() {
-        let stat = await OS.File.stat(xpiPath);
-        await OS.File.setDates(
-          xpiPath,
-          stat.lastAccessDate,
-          stat.lastModificationDate.valueOf() + 60 * 1000
-        );
+        let stat = await IOUtils.stat(xpiPath);
+        let newLastModTime = stat.lastModified + 60 * 1000;
+        await IOUtils.touch(xpiPath, newLastModTime);
       },
     },
   ];
@@ -104,16 +101,13 @@ add_task(async function run_tests() {
 
     await promiseShutdownManager();
 
-    let orig = await OS.File.stat(xpiPath);
+    let fileInfo = await IOUtils.stat(xpiPath);
 
     xpi2.copyTo(profileDir, `${ID}.xpi`);
 
-    // Make sure the timestamp is unchanged, so it is not re-scanned for that reason.
-    await OS.File.setDates(
-      xpiPath,
-      orig.lastAccessDate,
-      orig.lastModificationDate
-    );
+    // Make sure the timestamp of the extension is unchanged, so it is not
+    // re-scanned for that reason.
+    await IOUtils.touch(xpiPath, fileInfo.lastModified);
 
     await test.action();
 
diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_upgrade_incompatible.js b/toolkit/mozapps/extensions/test/xpcshell/test_upgrade_incompatible.js
index c109890080a1..70e40fa29b67 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_upgrade_incompatible.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_upgrade_incompatible.js
@@ -35,10 +35,10 @@ add_task(async function test_upgrade_incompatible() {
 
   // swap the incompatible extension in for the original
   let path = OS.Path.join(gProfD.path, "extensions", `${ID}.xpi`);
-  let sb = await OS.File.stat(path);
-  let timestamp = sb.lastModificationDate.valueOf();
+  let fileInfo = await IOUtils.stat(path);
+  let timestamp = fileInfo.lastModified;
 
-  await OS.File.move(newfile.path, path);
+  await IOUtils.move(newfile.path, path);
   await promiseSetExtensionModifiedTime(path, timestamp);
   Services.obs.notifyObservers(new FileUtils.File(path), "flush-cache-entry");
 
@@ -60,7 +60,7 @@ add_task(async function test_upgrade_incompatible() {
   });
 
   // swap the old extension back in and check that we don't persist the disabled state forever.
-  await OS.File.move(file.path, path);
+  await IOUtils.move(file.path, path);
   await promiseSetExtensionModifiedTime(path, timestamp);
   Services.obs.notifyObservers(new FileUtils.File(path), "flush-cache-entry");