diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0f1e7f2..3e5c5a0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 --- develop ---
 
+* issue#250: Fix date filter persistence by validating before shift_span detection
 * issue: Making changes to support Cacti 1.3
 * issue: Don't use MyISAM for non-analytical tables
 * issue: The install advisor for Syslog was broken in current Cacti releases
diff --git a/syslog.php b/syslog.php
index 185e0cd..50bd2e1 100644
--- a/syslog.php
+++ b/syslog.php
@@ -779,7 +779,7 @@ function syslog_request_validation($current_tab, $force = false) {
 function set_shift_span($shift_span, $session_prefix) {
 	global $graph_timeshifts;
 
-	if ($shift_span == 'span' || $shift_span === false) {
+	if ($shift_span == 'span' || ($shift_span === false && (!isset($_SESSION[$session_prefix . '_date1']) || !isset($_SESSION[$session_prefix . '_date2'])))) {
 		$span = array();
 
 		// Calculate the timespan
@@ -795,6 +795,21 @@ function set_shift_span($shift_span, $session_prefix) {
 		kill_session_var($session_prefix . '_date2');
 
 		set_request_var('custom', false);
+	} elseif ($shift_span === false) {
+		// Page navigation: custom dates were set earlier; restore from session.
+		if (isset($_SESSION[$session_prefix . '_date1']) && isset($_SESSION[$session_prefix . '_date2'])) {
+			set_request_var('date1', $_SESSION[$session_prefix . '_date1']);
+			set_request_var('date2', $_SESSION[$session_prefix . '_date2']);
+			set_request_var('custom', true);
+		} else {
+			// Session keys missing; fall back to a fresh span calculation.
+			$first_weekdayid = read_user_setting('first_weekdayid');
+			$span = array();
+			get_timespan($span, time(), get_request_var('predefined_timespan'), $first_weekdayid);
+			set_request_var('date1', date('Y-m-d H:i:s', $span['begin_now']));
+			set_request_var('date2', date('Y-m-d H:i:s', $span['end_now']));
+			set_request_var('custom', false);
+		}
 	} elseif ($shift_span == 'shift') {
 		$span = array();
 
@@ -826,6 +841,9 @@ function set_shift_span($shift_span, $session_prefix) {
 
 		set_request_var('custom', true);
 	} elseif ($shift_span == 'custom') {
+		// Persist custom dates so page navigation preserves the filter.
+		$_SESSION[$session_prefix . '_date1'] = get_request_var('date1');
+		$_SESSION[$session_prefix . '_date2'] = get_request_var('date2');
 		set_request_var('custom', true);
 	}
 }