diff --git a/mozilla/modules/libjar/nsJAR.cpp b/mozilla/modules/libjar/nsJAR.cpp
index 8467b66d304..d3dd2871a7a 100644
--- a/mozilla/modules/libjar/nsJAR.cpp
+++ b/mozilla/modules/libjar/nsJAR.cpp
@@ -798,7 +798,8 @@ nsJAR::RestoreModTime(nsZipItem *aItem, nsIFile *aExtractedFile)
   if (timestr)
   {
     if (PR_SUCCESS == PR_ParseTimeString(timestr, PR_FALSE, &prtime))
-      rv = aExtractedFile->SetLastModificationDate(prtime);
+        // nsIFile needs usecs.
+      rv = aExtractedFile->SetLastModificationDate(prtime / PR_USEC_PER_MSEC);
 
     JAR_NULLFREE(timestr);
   }
diff --git a/mozilla/xpcom/io/nsIFile.idl b/mozilla/xpcom/io/nsIFile.idl
index 2d851780482..23683b305f3 100644
--- a/mozilla/xpcom/io/nsIFile.idl
+++ b/mozilla/xpcom/io/nsIFile.idl
@@ -173,6 +173,11 @@ interface nsIFile : nsISupports
     attribute unsigned long permissions;
     attribute unsigned long permissionsOfLink;
     
+    /**
+     *  File Times are to be in Milliseconds (usecs) from 
+     *  midnight (00:00:00), January 1, 1970 Greenwich Mean 
+     *  Time (GMT).
+     */
     attribute PRInt64 lastModificationDate;
     attribute PRInt64 lastModificationDateOfLink;
     
diff --git a/mozilla/xpcom/io/nsLocalFileMac.cpp b/mozilla/xpcom/io/nsLocalFileMac.cpp
index aba6cd700ba..003d4325970 100644
--- a/mozilla/xpcom/io/nsLocalFileMac.cpp
+++ b/mozilla/xpcom/io/nsLocalFileMac.cpp
@@ -374,29 +374,29 @@ static void MacintoshInitializeTime(void)
     gJanuaryFirst1970Seconds = 2082844800 + GMTDelta();
 }
 
-static nsresult	ConvertMacTimeToUnixTime( PRInt64* aLastModificationDate, PRInt32 timestamp )
+static nsresult	ConvertMacTimeToMilliseconds( PRInt64* aLastModificationDate, PRInt32 timestamp )
 {
 	if ( gJanuaryFirst1970Seconds == 0)
 		MacintoshInitializeTime();
 	timestamp -= gJanuaryFirst1970Seconds;
-  PRTime			oneMillion, dateInMicroSeconds;
+    PRTime usecPerSec, dateInMicroSeconds;
 	LL_I2L(dateInMicroSeconds, timestamp);
-	LL_I2L(oneMillion, 1000000UL);
-	LL_MUL(*aLastModificationDate, oneMillion, dateInMicroSeconds);
+	LL_I2L(usecPerSec, PR_USEC_PER_SEC);
+	LL_MUL(*aLastModificationDate, usecPerSec, dateInMicroSeconds);
 	return NS_OK;
 }
 
-static nsresult ConvertUnixTimeToMacTime(PRInt64 aUnixTime, PRUint32 *aOutMacTime)
+static nsresult ConvertMillisecondsToMacTime(PRInt64 aTime, PRUint32 *aOutMacTime)
 {
 	NS_ENSURE_ARG( aOutMacTime );
 		
-	PRTime oneMillion, dateInSeconds;
+	PRTime usecPerSec, dateInSeconds;
 	dateInSeconds = LL_ZERO;
 	
-	LL_I2L(oneMillion, 1000000UL);
-	LL_DIV(dateInSeconds, aUnixTime, oneMillion); // dateInSeconds = aUnixTime/1,000,000
+	LL_I2L(usecPerSec, PR_USEC_PER_SEC);
+	LL_DIV(dateInSeconds, aTime, usecPerSec); // dateInSeconds = aTime/1,000
 	LL_L2UI(*aOutMacTime, dateInSeconds);
-	*aOutMacTime += 2082844800; // dateInSeconds + Mac epoch
+	*aOutMacTime += 2082844800; // date + Mac epoch
 	
 	return NS_OK;
 }
diff --git a/mozilla/xpcom/io/nsLocalFileUnix.cpp b/mozilla/xpcom/io/nsLocalFileUnix.cpp
index c4512e8e3df..c5a0b06d1c4 100644
--- a/mozilla/xpcom/io/nsLocalFileUnix.cpp
+++ b/mozilla/xpcom/io/nsLocalFileUnix.cpp
@@ -827,7 +827,8 @@ nsLocalFile::GetLastModificationDate(PRInt64 *aLastModificationDate)
         return NSRESULT_FOR_ERRNO();
     }
     // PRTime is a 64 bit value
-    *aLastModificationDate = info.modifyTime;
+    // microseconds -> milliseconds
+    *aLastModificationDate = info.modifyTime / PR_USEC_PER_MSEC;
     return NS_OK;
 }
 
@@ -843,7 +844,7 @@ nsLocalFile::SetLastModificationDate(PRInt64 aLastModificationDate)
         // convert PRTime microsecs to unix seconds since the epoch
         double dTime;
         LL_L2D(dTime, aLastModificationDate);
-        ut.modtime = (time_t)( (PRUint32)(dTime * 1e-6 + 0.5) );
+        ut.modtime = (time_t)( (PRUint32)(dTime / PR_MSEC_PER_SEC) );
         result = utime(mPath, &ut);
     } else {
         result = utime(mPath, NULL);
@@ -860,6 +861,10 @@ nsLocalFile::GetLastModificationDateOfLink(PRInt64 *aLastModificationDateOfLink)
     if (lstat(mPath, &sbuf) == -1)
         return NSRESULT_FOR_ERRNO();
     mLL_II2L(0, (PRUint32)sbuf.st_mtime, *aLastModificationDateOfLink);
+
+    // lstat returns st_mtime in seconds!
+    *aLastModificationDate *= PR_MSEC_PER_SEC;
+
     return NS_OK;
 }
 
diff --git a/mozilla/xpcom/io/nsLocalFileWin.cpp b/mozilla/xpcom/io/nsLocalFileWin.cpp
index 38460e6a644..358cf6ddc74 100644
--- a/mozilla/xpcom/io/nsLocalFileWin.cpp
+++ b/mozilla/xpcom/io/nsLocalFileWin.cpp
@@ -1175,7 +1175,8 @@ nsLocalFile::GetLastModificationDate(PRInt64 *aLastModificationDate)
     if (NS_FAILED(rv))
         return rv;
     
-    *aLastModificationDate = mFileInfo64.modifyTime;
+    // microseconds -> milliseconds
+    *aLastModificationDate = mFileInfo64.modifyTime / PR_USEC_PER_MSEC;
     return NS_OK;
 }
 
@@ -1192,7 +1193,9 @@ nsLocalFile::GetLastModificationDateOfLink(PRInt64 *aLastModificationDate)
     if (NS_FAILED(rv))
         return rv;
     
-    *aLastModificationDate = mFileInfo64.modifyTime;
+    // microseconds -> milliseconds
+    *aLastModificationDate = mFileInfo64.modifyTime / PR_USEC_PER_MSEC;
+
     return NS_OK;
 }
 
@@ -1238,8 +1241,9 @@ nsLocalFile::SetModDate(PRInt64 aLastModificationDate, PRBool resolveTerminal)
     FILETIME lft, ft;
     SYSTEMTIME st;
     PRExplodedTime pret;
-
-    PR_ExplodeTime(aLastModificationDate, PR_LocalTimeParameters, &pret);
+    
+    // PR_ExplodeTime expects usecs...
+    PR_ExplodeTime(aLastModificationDate * PR_USEC_PER_MSEC, PR_LocalTimeParameters, &pret);
     st.wYear            = pret.tm_year;    
     st.wMonth           = pret.tm_month + 1; // Convert start offset -- Win32: Jan=1; NSPR: Jan=0
     st.wDayOfWeek       = pret.tm_wday;