Open Radar

 
Area:
Something not on this list

Summary:
In Settings>General>Language & Region, setting the calendar to Japanese instead of Gregorian breaks the display of dates and time across the whole system (both iOS and watchOS). I don't know how to categorize this issue or if I need to make multiple, please advise.

Steps to Reproduce:
Go to Settings>General>Language & Region, set the Calendar to Japanese instead of Gregorian (didn't try Buddhist, but should worth a check from your side), especially while keeping the iPhone language to English.

Expected Results:
To work the same as it always did since my first iPhone a decade ago, display all dates and times correctly, as well as correctly calculate date difference ("yesterday", "X days ago", etc)

Actual Results:
- Multiple bugs depending on the format, short format displays "(minutes)", "(seconds)" etc, with numbers overwriting the words, for ex: "(05inutes)", this appears in Timers such as the Clock app and Music App when playing a song for remaining time.
- In the Clock app and elsewhere, same problems, but also no AM/PM display for 12h clock, making it impossible to know what time an alarm is set to.
- The weather app doesn't respect the 12/24 hours setting on sunrise/sunset positions.
- Long formats are broken, for example the current Japanese year is 29H (Heisei), but it displays 0029, etc.
- Other formats display weird dates, such as the Health App that displays the year as 678 in the graph view, but correctly everywhere else in the app.
- Date differences are completely broken, for example, the Music App displays "-1,452,201 Days Ago" for a mix that is a couple days old.
* Note: Outside of the last bug in the Music App, none of these problems existed in prior versions of iOS.

Version/Build:
iOS 11 betas through the final release 11.0 (15A372)

Configuration:
Multiple iPhones (6s, 7s+), iPads (Air, Pro 12.9") and Apple Watch Series 2