diff --git a/TimeSeries.pm b/TimeSeries.pm
index 2933fcf..0556a51 100644
--- a/TimeSeries.pm
+++ b/TimeSeries.pm
@@ -553,7 +553,7 @@ sub get_ticks {
 	$sec = $min = $hour = 0;
 	$mday = 1;
 	$mon = 0;
-        $year = floor($year / 5) * 5;
+        $year = floor(($year + 1900) / 5) * 5;
 	$firsttime = timelocal($sec,$min,$hour,$mday,$mon,$year);
 
 	$label = '%Y-%m-%d';