diff --git a/distfiles/schedmaint.php b/distfiles/schedmaint.php
index ee90f2e..00f988d 100644
--- a/distfiles/schedmaint.php
+++ b/distfiles/schedmaint.php
@@ -75,7 +75,7 @@ if ($action) {
         // sanitize user input
         $completedate = fix_date($completedate);
         // update events
-        mysqli_query($db, "update events set last_date=\"$completedate\", deferred_flag=0, deferred_date=\"0000-00-00\" where eventid=\"$id\"");
+        mysqli_query($db, "update events set last_date=\"$completedate\", deferred_flag=0, deferred_date=\"0001-01-01\" where eventid=\"$id\"");
         if ($addlognote) {
             $compltaskname = mysqli_fetch_row(mysqli_query($db, "select tasks.taskname from tasks,events where events.eventid=\"$id\" and tasks.taskid=events.task"))[0];
             $compldevicename = mysqli_fetch_row(mysqli_query($db, "select devices.devicename from devices,events where events.eventid=\"$id\" and devices.deviceid=events.device"))[0];
@@ -490,8 +490,8 @@ if ($action) {
     while ($tablerow = mysqli_fetch_assoc($existingdata)) {
         extract($tablerow);
         if ($start_date == "0001-01-01") $start_date = $today;
-        if ($last_date == "0000-00-00") $last_date = "";
-        if ($deferred_date == "0000-00-00") $deferred_date = "";
+        if ($last_date == "0001-01-01") $last_date = "";
+        if ($deferred_date == "0001-01-01") $deferred_date = "";
         if ($active_flag) {
             $statdef = "<img src=\"icons/tick.png\" title=\"active\" alt=\"active\">";
         } else {
@@ -857,7 +857,7 @@ if ($action) {
         $taskdata = mysqli_fetch_assoc(mysqli_query($db, "select * from tasks where taskid=\"$def_task\""));
         extract($taskdata, EXTR_PREFIX_ALL, "taskdata");
         if (! ($taskdata_period == "once" && $def_last_date > $def_start_date)) {
-            if ($def_last_date == "0000-00-00") {
+            if ($def_last_date == "0001-01-01") {
                 $lastdatestrg = "never";
             } else {
                 $lastdatestrg = "$def_last_date";