diff options
Diffstat (limited to 'modules/calendar-sync-recurrence.el')
| -rw-r--r-- | modules/calendar-sync-recurrence.el | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/modules/calendar-sync-recurrence.el b/modules/calendar-sync-recurrence.el index a3bd4dc4..9ef12ce5 100644 --- a/modules/calendar-sync-recurrence.el +++ b/modules/calendar-sync-recurrence.el @@ -498,11 +498,27 @@ DTSTART's month, landing each occurrence on the day its BYDAY rule selects BASE-EVENT is the event plist, RRULE is parsed rrule, RANGE is date range. A rule with BYDAY (nth weekday, e.g. 2WE, -1TU, or SU with BYSETPOS) expands via `calendar-sync--expand-monthly-byday'; a plain rule steps -DTSTART's day-of-month." +DTSTART's day-of-month, skipping months without that day." (if (plist-get rrule :byday) (calendar-sync--expand-monthly-byday base-event rrule range) (calendar-sync--expand-simple-recurrence - base-event rrule range #'calendar-sync--add-months))) + base-event rrule range #'calendar-sync--next-monthly-date))) + +(defun calendar-sync--next-monthly-date (date interval) + "Step DATE forward INTERVAL months, skipping months without DATE's day. +A plain FREQ=MONTHLY on the 31st must skip short months (RFC 5545): +`calendar-sync--add-months' keeps day-of-month verbatim, so Jan 31 would +step to Feb 31, which encode-time normalizes into a phantom Mar 3 +occurrence. Bounded so a pathological input can't loop forever." + (require 'time-date) + (let ((next (calendar-sync--add-months date interval)) + (day (nth 2 date)) + (guard 0)) + (while (and (< guard 100) + (> day (date-days-in-month (nth 0 next) (nth 1 next)))) + (setq guard (1+ guard)) + (setq next (calendar-sync--add-months next interval))) + next)) (defun calendar-sync--expand-yearly-byday (base-event rrule range) "Expand a yearly nth-weekday event (e.g. BYMONTH=3;BYDAY=2SU). |