diff --git a/browser/base/content/aboutStartup.js b/browser/base/content/aboutStartup.js
index e591a4f75976..bc6f9ba929db 100755
--- a/browser/base/content/aboutStartup.js
+++ b/browser/base/content/aboutStartup.js
@@ -4,4 +4,4 @@ var Ci = Components.interfaces;
 var runtime = Cc["@mozilla.org/xre/runtime;1"]
                 .getService(Ci.nsIXULRuntime);
 var started = document.getElementById("started");
-started.textContent = runtime.startupTimestamp
+started.textContent = new Date(runtime.startupTimestamp/1000) +" ("+ runtime.startupTimestamp +")";
diff --git a/toolkit/xre/nsAppData.cpp b/toolkit/xre/nsAppData.cpp
index f10ea45558bf..dc74b77904de 100755
--- a/toolkit/xre/nsAppData.cpp
+++ b/toolkit/xre/nsAppData.cpp
@@ -73,7 +73,7 @@ ScopedAppData::ScopedAppData(const nsXREAppData* aAppData)
   this->size = aAppData->size;
 
   if (aAppData->size > offsetof(nsXREAppData, startupTimestamp)) {
-    this->startupTimestamp = PR_IntervalNow();
+    this->startupTimestamp = PR_Now();
   }
 
   SetAllocatedString(this->vendor, aAppData->vendor);
diff --git a/toolkit/xre/nsAppRunner.cpp b/toolkit/xre/nsAppRunner.cpp
index 1d6d07624986..e7c4f729bbfa 100755
--- a/toolkit/xre/nsAppRunner.cpp
+++ b/toolkit/xre/nsAppRunner.cpp
@@ -806,13 +806,13 @@ nsXULAppInfo::InvalidateCachesOnRestart()
 }
 
 /* readonly attribute unsigned long launchTimestamp; */
-NS_IMETHODIMP nsXULAppInfo::GetLaunchTimestamp(PRUint32 *aTimestamp)
+NS_IMETHODIMP nsXULAppInfo::GetLaunchTimestamp(PRUint64 *aTimestamp)
 {
     return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 /* readonly attribute unsigned long startupTimestamp; */
-NS_IMETHODIMP nsXULAppInfo::GetStartupTimestamp(PRUint32 *aTimestamp)
+NS_IMETHODIMP nsXULAppInfo::GetStartupTimestamp(PRUint64 *aTimestamp)
 {
   *aTimestamp = gAppData->startupTimestamp;
   return NS_OK;
diff --git a/xpcom/build/nsXULAppAPI.h b/xpcom/build/nsXULAppAPI.h
index 8cb0197bfc70..23bed5f06c15 100755
--- a/xpcom/build/nsXULAppAPI.h
+++ b/xpcom/build/nsXULAppAPI.h
@@ -155,7 +155,7 @@ struct nsXREAppData
   /**
    * 
    */
-  PRIntervalTime startupTimestamp;
+  PRTime startupTimestamp;
 };
 
 /**
diff --git a/xpcom/system/nsIXULRuntime.idl b/xpcom/system/nsIXULRuntime.idl
index c2a6e60bc4cd..745cfc679cd8 100755
--- a/xpcom/system/nsIXULRuntime.idl
+++ b/xpcom/system/nsIXULRuntime.idl
@@ -108,6 +108,6 @@ interface nsIXULRuntime : nsISupports
    */
   void invalidateCachesOnRestart();
 
-  readonly attribute unsigned long launchTimestamp;
-  readonly attribute unsigned long startupTimestamp;
+  readonly attribute unsigned long long launchTimestamp;
+  readonly attribute unsigned long long startupTimestamp;
 };