[Bug] TimePicker posts 12-hour formatted value in the UI control when device setting is 24-hour format

[irinakush]

Description

Locale: en-AU
TimePicker.Format is not set (= default)

TimePicker picker/dialog respects device settings (24/12-hour format). However, when TimePicker posts value from the picker/dialog into the control, value appears in the 12-hour format regardless of the device setting.

It doesn't look like iOS ever worked but for Android it looks like Fix datetimepickerlocalization caused a regression of [Android] Use 24-hour time format on TimePicker text if enabled (#1082)

Suggestion

Make a default TimePicker.Format an empty value.
When TimePicker.Format is empty, check device settings for 12/24-hour format and use format accordingly.

Example for Android:
Xamarin.Forms/Xamarin.Forms.Platform.Android/Renderers/TimePickerRenderer.cs

		void SetTime(TimeSpan time)
		{
			var timeFormat = Element.Format;		
			if (String.IsNullOrEmpty(timeFormat))
			{
				timeFormat = (DateFormat.Is24HourFormat(Context) ? "HH:mm" : "h:mm tt";
			}
			EditText.Text = DateTime.Today.Add(time).ToString(timeFormat);

			Element.InvalidateMeasureNonVirtual(Internals.InvalidationTrigger.MeasureChanged);
		}

Steps to Reproduce

1. Drop on the form. Or use TimePicker sample from the Xamarin-Forms-Samples
2. Set device time to 24-hour format (Android or iOS)
3. Run the project.
4. Tap on the picker
5. Select 17:00

Expected Behavior

Value posted into control is 17:00.

Actual Behavior

Value posted into control is 5:00 PM.

Basic Information

• Version with issue: 5.0.0
• Last known good version: 4.8.0 (Android)
• Platform Target Frameworks:
  • iOS: 14.3
  • Android: 10
• Affected Devices: Pixel XL, iPhone 11

Environment

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Microsoft Visual Studio Professional 2019
Version 16.9.3
VisualStudio.16.Release/16.9.3+31129.286
Microsoft .NET Framework
Version 4.8.04084

Installed Version: Professional

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Xamarin.iOS and Xamarin.Mac SDK   14.14.2.5 (3836759d4)
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Build Logs

n/a

Screenshots

Reproduction Link

Xamarin-Forms-Samples

Workaround

Check the device 12/24-hour setting and assign "h:mm tt"/"HH:mm" value to TimePicker.Format.

[irinakush]

Posted as a question in MS Q&A instead.