datepicker: startAt and setting value doesn't work correctly

[fxck]

repro (using mmalerba:dp-a11y):

• predefine value to 2017-05-02 (YYYY-MM-DD), input shows correctly 02/05/2017
• open datepicker, it opens on a wrong month (second, instead of the fifth)
• select 6th day of the second month (that was open), input changes to 06/02/2017 (should have been 06/05/2017)
• close and open input again, selected day is set to second of february, but calendar opens at sixth month

@mmalerba

[mmalerba]

This is a limitation of the native JS Date object since It's not possible to set a parse format. We are planning to add a MomentDateAdapter soon (and corresponding MD_MOMENT_DATE_FORMATS) that will work with moment.js, a library that has more robust date parsing and formatting.

If you don't want to use moment, it's easy to write your own adapter for whatever date implementation you want

[fxck]

Hmm, right. I've already written my own date-fns adapter, but apparently it cannot parse different formats either... yet anyway - date-fns/date-fns#375

But doesn't this basically mean that you won't able to use locale out of the box unless you use momentjs, which is absolutely humongous untreeshakable lib? Wouldn't it be worth shipping with an adapter that can do actually this?

[mmalerba]

Happy to consider adding adapters for other implementations, but implementing robust internationalized date parsing and formatting is outside the scope of Angular Material. NativeDateAdapter is provided for users who need a very basic implementation that doesn't depend on any additional libraries, but in most cases people will want to use the moment adapter or create their own.

[mmalerba]

Closing this since its WAI for NativeDateAdapter.

[fxck]

@mmalerba these issues will keep piling on, I think it would be worth adding some all caps bold statement to calendar docs that it doesn't support any other locale than those with MM-DD-YYYY formats.