From 2be32c4bda5236ec19e0f3c544adcd2974684f50 Mon Sep 17 00:00:00 2001
From: Lars Henriksen <LarsHenriksen@get2net.dk>
Date: Sat, 27 Apr 2019 23:28:52 +0200
Subject: Impossible dates in recurrence rules
According to RFC 5545 dates like 30 February and 31 June must be ignored
when derived from a recurrence rule.
calcurse relies on mktime() "normalization" of dates (e.g. turning 32
December 2019 into 1 January 2020 when moving from 31 December to the
next day).
Normalization may also lead to impossible dates in monthly and yearly
recurrence rules, and this must be avoided.
Signed-off-by: Lars Henriksen <LarsHenriksen@get2net.dk>
Signed-off-by: Lukas Fleischer <lfleischer@calcurse.org>
---
src/recur.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
(limited to 'src')
diff --git a/src/recur.c b/src/recur.c
index 4e8bd09..46f669d 100644
--- a/src/recur.c
+++ b/src/recur.c
@@ -815,6 +815,18 @@ recur_item_find_occurrence(time_t item_start, long item_dur,
lt_item_day.tm_isdst = lt_day.tm_isdst;
t = mktime(<_item_day);
+ /*
+ * Impossible dates must be ignored (according to RFC 5545). Changing
+ * only the year or the month may lead to dates like 29 February in
+ * non-leap years or 31 November.
+ */
+ if (rpt_type == RECUR_MONTHLY || rpt_type == RECUR_YEARLY) {
+ localtime_r(&t, <_item_day);
+ if (lt_item_day.tm_mday != lt_item.tm_mday)
+ return 0;
+ }
+
+ /* Exception day? */
if (LLIST_FIND_FIRST(item_exc, &t, exc_inday))
return 0;
--
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