Implement iCal data export

[arkid15r]

I wanna add my country's holidays to google calendar. Is it possible?
Google calendar supports iCal.

Based on #2160

[kawazap]

Hi, @arkid15r
I am Winter of Code's Contributor❄
I'm interested in implementing iCal export functionality (#2179) and I would be able to learn a lot If I could work on this project.
Before submitting my proposal, I have a few questions about the implementation details!

1. Library Dependencies

• Is it acceptable to use the icalendar package for the implementation?
• Or should we create a minimal custom solution to avoid additional dependencies?

2. Internationalization
   Since the holidays framework already supports i18n for holiday names, I'm considering adding language support for iCal export:

holidays.JP().to_ical(language='en')  # Export in English

Would this approach align with the project's direction?
3. Date Handling
For holiday dates, I'm planning to use simple DATE format without time information:

DTSTART;VALUE=DATE:20240101

Are there any cases where we would need time/timezone handling?
Thanks for your guidance!

[arkid15r]

Hi @kawazap, thanks for your interest to the project as a part of WoC 4.0!

1. We worked hard to minimize the dependencies list to a single item (dateutil) and would prefer not to introduce new dependencies if a task can be done w/o it.
2. It'd be great to have holidays l10n support for ical too 👍
3. Yes, that's what we have right now and your plan sounds good to me -- we don't have time/timezone support atm.

Please let me know if you have followup questions.

[kawazap]

@arkid15r
Thank you for your prompt and clear feedback!

After sorting through your feedback and iCal export requirements, I understand that

1. a simple custom implementation that does not introduce new dependencies is the best approach
2. very little iCal functionality is required for holiday export:
   • Basic event creation
   • DATE format without handling time/timezone
   • Integration with existing internationalisation support
3. this fits nicely with the framework's commitment to minimal dependencies (only dateutil).

I will proceed to develop a detailed proposal focused on a lightweight custom implementation covering these requirements.

Thank you for your guidance!

[arkid15r]

It seems we're on the same page!

Please consider adding localization related contributions or your native country holidays improvement too as WoC is a month long event. Also feel free to suggest your own ideas in the proposal.

Thank you for choosing us for your WoC proposal @kawazap

[kawazap]

@arkid15r
Thanks for the feedback! I'm glad we're aligned on the direction 😊

I checked the Japanese holidays implementation and it seems pretty well maintained. If I find any issues with Japanese holidays during the project, I'll prioritize those. Otherwise, I'm thinking of helping with countries that don't have holiday support yet when I have extra time.

I'll work on polishing up the proposal tonight!