Apple used to maintain its own set of calendars, but that page no longer exists, and recently my subscription for Vietnamese holidays (pulled from Apple’s now-retired page) stopped updating in the Calendar app.
It’s easy enough to derive certain countries’ holiday subscriptions from the US one. For instance you can subscribe to French holidays at https://p20-calendars.icloud.com/holiday/FR_fr.ics. However there doesn’t seem to be one at https://p20-calendars.icloud.com/holiday/VN_vn.ics.
Does anyone have the address for Apple’s Vietnamese holiday calendar? I realize there may be other sites that offer such calendars, but I’d prefer to use Apple’s.