The specified value does not conform to the required format yyyy-MM-dd

Question

The specifications for the HTML5 date picker state that the date must be in the format yyyy-MM-dd (ISO format). This means that you DisplayFormatAttribute must be

[DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
public string MyDate { get; set; }

Alternatively you can manually add the format using

@Html.TextBoxFor(m => m.MyDate, "{0:yyyy-MM-dd}", new { @type = "date"  })

The later option allows you to keep the DataFormatString = "{0:dd/MM/yyyy}") for usage in @Html.DisplayFor()

The issue could be from the type="date". That was my situation anyway. Worked once it was changed to type="text". If the interface is built with an MVC wrapper, you need to replace or set the html attribute accordingly.

You can use the InputTagHelper.Format

<input asp-for="MyDate" asp-format="{0:yyyy-MM-dd}" />

https://docs.asp.net/projects/api/en/latest/autoapi/Microsoft/AspNetCore/Mvc/TagHelpers/InputTagHelper/#prop-Microsoft.AspNetCore.Mvc.TagHelpers.InputTagHelper.Format

Set the type attribute to text.

@Html.TextBoxFor(m => m.MyDate, new { @type = "text"  })