asp.net mvc datetime dynamic validation by clients date format

If you can determine the locale of your user, you can use .Net globalization classes to assist with server-side parsing of date time strings. For example:

// Parsed as January 4th
var dt1 = DateTime.Parse("1/4/2013", new CultureInfo("en-US"));

// Parsed as April 1st
var dt2 = DateTime.Parse("1/4/2013", new CultureInfo("en-GB"));

But the best thing to do is avoid this entirely. In your JavaScript code, get the value back as an ISO8601 string - which is culture invariant. Native browser support for this varies. The built-in functions work in IE9+.

// This returns an ISO formatted date, in UTC.
var s = yourDate.ToISOString();

One way to get full browser support, and get an ISO date without converting to UTC, is to use the moment.js library, where ISO8601 is the default format:

// This returns an ISO formatted date, with the user's local offset.
var s = moment(yourDate).format();

// This returns an ISO formatted date, in UTC.
var s = moment(yourDate).utc().format();

When you send these values to the server, you can parse them in your .Net code without concern for culture. The format is already culture invariant. To prevent the server's time zone from interfering, you should parse them as a DateTimeOffset:

// assuming this is an ISO value you got from the client:
var s = "2013-04-20T09:00:00-07:00";

// simply parse it
var dto = DateTimeOffset.Parse(s);

// if you don't care about the offset at this point:
var dt = dto.DateTime;

Of course, if you want to fail gracefully, you can do this instead:

DateTimeOffset dto;
var isValid = DateTimeOffset.TryParse(s, out dto);