datepicker: modifies time

Bug

Demo and steps to reproduce the issue

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Detailed Reproduction Steps

1. Notice the date strings have some time values
2. Click or focus the datepicker
3. Notice that the date strings have all of their time values set to midnight

Explain the expected behavior

The ng-model value must to remain the predefined time as far as possible.

However, regarding the limits (md-min-date and md-max-date), they have to be treat as read-only data, not altered.

Explain the current behavior

In the last updates, when date picker is interacted (clicked, calendar showed, focused...), time of scope values are changed. It happens both to ng-model and to limits (md-min-date and md-max-date). It is very traumatic when you are using these values to control datetime by another time input.

Discuss the use-case or motivation for changing the existing behavior

List the affected versions of AngularJS, Material, OS, and browsers

• AngularJS: 1.7.2
• AngularJS Material: 1.2.1
• OS: macOS
• Browsers: Chrome 85
• Screen Readers:

Add anything else we should know

Stack Trace

N/A

Screenshots

[Splaktar]

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[Splaktar]

Yes, the times are set to midnight as the datepicker only works with dates and not times.

I can see that your demo shows the times being set to midnight when an interaction with the datepicker happens. I added reproduction steps to the issue. But can you explain the impact of this in a wider use case? There is an expected behavior section of the issue template and a use case discussion section of the template that are required and helpful when analyzing issue reports.

The impact of this? I already said: "It is very traumatic when you are using these values to control datetime by another time input". Test a library to insert time using the same datetime limits and check that this "expected behavior" turns something simple into a headache.