bug: Monthly recurrence for yearly events when BYMONTHDAY is used

[alexgit2k]

Describe the bug If not only "FREQ=YEARLY" is set for yearly events, but also the parameter "BYMONTHDAY=..." - like the Windows 10 calendar app is doing - then recurring_ical_events converts them to monthly events.

To Reproduce

#!/usr/bin/python3

import icalendar, recurring_ical_events_master

start_date = (2020, 7, 1)
end_date = (2020, 10, 1)
file = 'test.ics'

ical_string = open(file,'r').read();
calendar = icalendar.Calendar.from_ical( ical_string )
events = recurring_ical_events_master.of(calendar).between(start_date, end_date)
for event in events:
    print("{} {}".format(event["DTSTART"].dt, event["SUMMARY"]))

ICS file

BEGIN:VCALENDAR
VERSION:2.0
CALSCALE:GREGORIAN

BEGIN:VEVENT
DTSTART;VALUE=DATE:20200716
DTEND;VALUE=DATE:20200717
RRULE:FREQ=YEARLY;WKST=MO;INTERVAL=1;BYMONTHDAY=16
SUMMARY:Yearly Birthday Wrong
END:VEVENT

BEGIN:VEVENT
DTSTART;VALUE=DATE:20200716
DTEND;VALUE=DATE:20200717
RRULE:FREQ=YEARLY
SUMMARY:Yearly Birthday Okay
END:VEVENT

END:VCALENDAR

Expected behavior Events with frequency yearly should still be yearly.

Console output

2020-07-16 Yearly Birthday Wrong
2020-08-16 Yearly Birthday Wrong
2020-09-16 Yearly Birthday Wrong
2020-07-16 Yearly Birthday Okay

Version: master-Branch (v0.1.18b + further commits)

[niccokunzmann]

Hi @alexgit2k and thanks for reporting this. To see where the issue lies, I think, the next step would be to feed the string FREQ=YEARLY;WKST=MO;INTERVAL=1;BYMONTHDAY=16 to the rrulestr function of dateutil and see if it provides the correct values. If yes, the bug is here. If not, the bug is in dateutil.rrule.

from dateutil.rrule import rrulestr

[alexgit2k]

You were right, its an error in rrulestr of dateutil. I reported it there: dateutil/dateutil/issues/1072

Thanks, closing this issue.