recurring calendar entries - more possibilities (e.g. every 4 weeks)

Great proposal and commit! Thank you!

Yay, thanks.
Looks way more polished than the default!

But is not the 3rd Monday of a month a bit too specific or? ;)

@peterleinchen That was why I ended up putting "from : Monday 20 April" at the top under recurring. I felt that it made the specific options "Third monday of the month" seem natural, and not jarring, when you were reminded of the start day being Monday.

A second reason is that I found it is quite easy to inadvertently make a new recurring event thinking you are basing it from today, but the calendar was showing another day completely. By reminding you of the base day and date, this is less likely.

@peterleinchen the "third Monday every month" is quite dynamic, depending on the choice of date for the event. It allows to register something like "I have meeting every second Thursday of every month at...". It's like @anandrkris was mentioning in his other thread.

@bongo This is a first attempt of implementation. I'm going to wait for the review comments to see what to improve. At the beginning, I prefer not to change too much the code in the closed parts, first because it's closed and I'm loosing rights on it, and second because, at the end Jolla needs to accept it and nothing is forcing them ;) So the simpler change, the higher chance of acceptation is. At the moment, it's just simple additions for both menuitem entries and addition of the day selector, so easy to review. That being said, I'm thinking about bigger changes, to reimplement the recurring choice page completely and not like a built-in ComboBox, so I can add a pull-down menu or embed the day selection withinthe "selected days" entry. The pull down menu may be used to tune the frequency (and thus the choice labels) with something like "simple recurrences - every two times - every three times". This way keeps the UI simple, but force the frequency to three at maximum to avoid populating the menu too much. What do you think ? Is it worth ?

Oh, I forgot, I need to add the "Every x days before the end of the month" entry. But this one annoys me a bit UI-wise. Indeed, this one would be hidden if the date for the event is not within, let say 7 days to the end of the month. So what should happen if a user select the last day for its event and choose the "Every last day of the month", but decides that the day should not be this one, but in the middle of the month instead. The recurring choice entry will then be hidden. What should it fallback to ? No recurrence ? Every month, same date ?

@Damien Caliste
Thanks for the edit of your above answer (and the work involved!).