Perl uses the 'ne' operator to compare strings, not the != operator.

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--- Scoop/Calendar.pm.orig	2007-10-30 01:15:32.000000000 -0600
+++ Scoop/Calendar.pm	2007-10-30 01:17:11.000000000 -0600
@@ -894,7 +894,7 @@
 			push @{$S->{CALENDAR_DAY_CACHE}->{$event->{cal_id}}->{$event->{date_end}}}, $event->{eid};
 			warn "  (_get_months_events) adding event $event->{eid}'s end date ($event->{date_end}) to the cache" if $DEBUG;
 		}
-		if ( $event->{date_start} && $event->{date_end} != '0000-00-00' ) {
+		if ( $event->{date_start} && $event->{date_end} ne '0000-00-00' ) {
 			my @date_start = split(/-/,$event->{date_start});
 			my @date_end = split(/-/,$event->{date_end});
 			my $Dd = Date::Calc::Delta_Days($date_start[0],$date_start[1],$date_start[2],@date_end);