when will apple finally implement full support for alternative calendars ?

Hello,

You mentioned workarounds being problematic but without knowing what workarounds you have tried I wanted to provide some incase one may work for you. I also want to include Apples Feedback page which would be the best place to request a feature like this.

This is a macOS article because it gives more detail than the iOS one but it can be achieved on either OS.

Use a Chinese, Hebrew, or Islamic lunar calendar on Mac - Apple Support

"Use a Chinese, Hebrew, or Islamic lunar calendar on Mac

The Calendar app supports showing Chinese, Hebrew, and Islamic lunar calendars. When you turn on a lunar calendar, the lunar calendar dates are listed along with their Gregorian calendar equivalents. The first day of a lunar month is marked with a thin red line. The first day of a lunar year is marked with a thick red line.

You can also view lunar calendar birthdays and holidays."

Import or export calendars on Mac - Apple Support

"Import events from a calendar file

You can import the events saved in a calendar (.ics) file. You can use this method to transfer calendar events in the On My Mac section of your calendar list to iCloud, merge events with a pre-existing calendar, or transfer calendar events to another device.

1. In the Calendar app  on your Mac, if needed, create a new calendar for the events.
2. Do any of the following:

• • Drag the exported calendar file into Calendar.
  • Choose File > Import, select the exported calendar file, then click Import.

1. Select the calendar to add the events to, then click OK.
2. Note: Importing a calendar file removes the event’s previous custom color."

Subscribe to calendars on Mac - Apple Support

"Subscribe to a calendar

To subscribe to a calendar from a link on the internet or an email you received, click the link. If you do this, you can skip step 1, and the calendar’s web address is filled out for you in step 2.

1. In the Calendar app  on your Mac, choose File > New Calendar Subscription.
2. Enter the calendar’s web address, then click Subscribe.
3. Enter a name for the calendar in the Name field, then click the adjacent pop-up menu and choose a color.
4. Click the Location pop-up menu, then choose an account for the subscription.

• • If you choose your iCloud account, the calendar is available on all your computers and devices that are set up with iCloud.
  • If you choose On My Mac, the calendar is saved on your computer.

1. To get the calendar’s event attachments or alerts, deselect the appropriate Remove checkboxes.
2. Click the Auto-refresh pop-up menu, then choose how often to update the calendar.
3. To prevent alerts from appearing for this calendar, select “Ignore alerts.”
4. Click OK.
5. To make changes later, click the name of the calendar, then choose Edit > Get Info."

Feedback - Calendar - Apple

I hope this helps.

This is a user-to-user forum. No one here can answer a “why” or “when” question. Although Apple administers this Apple Support Communities site, that doesn't include reading each of thousands of daily posts for possible feedback. However, Apple will read all feedback carefully here: https://apple.com/feedback

Also, you post is almost meaninglessly general. It would be very helpful if you gave some specific examples of calendars that you would like to see. Currently iPhones support Gregorian, Japanese and Buddhist calendars in the US and European versions, plus appropriate calendars when the phone is set to other regions and countries. The default US Holidays calendar includes holidays for the 5 most commonly practiced religions in the US, and there are hundreds of specialized subscription calendars that can be downloaded from the internet for holidays in other regions and countries.