I have been reading that if you want to convert from JavaScript dates to C# dates you should use getTime() and then add that result to a C# DateTime.
Suppose I have this JavaScript time:
Date {Tue Jul 12 2011 16:00:00 GMT-0700 (Pacific Daylight Time)}
It renders to 1310522400000 milliseconds
var a = new DateTime(1970, 01, 01).AddMilliseconds(1310522400000);
// result
7/13/2011 2:00:00 AM
So this is wrong. I am not sure what I need to do.
If you want to send dates to C# from JS that is actually quite simple - if sending UTC dates is acceptable.
var date = new Date("Tue Jul 12 2011 16:00:00 GMT-0700");
var dateStrToSendToServer = date.toISOString();
... send to C# side ...
var success = DateTimeOffset.TryParse(jsISOStr, CultureInfo.InvariantCulture, DateTimeStyles.AssumeUniversal, out var result);
C# DateTime already understands ISO date formats and will parse it just fine.
To format from C# to JS just use DateTime.UtcNow.ToString("o").
Personally, I'm never comfortable relying on math and logic between different environments to get the milliseconds/ticks to show the EXACT same date and time a user may see on the client (especially where it matters). I would do the same when transferring currency as well (use strings instead to be safe, or separate dollars and cents between two different integers). Sending the date/time as separate values would be just a good (see accepted answer).
UPDATE: From .NET Version 4.6 use the FromUnixTimeMilliseconds method of the DateTimeOffset structure instead:
DateTimeOffset.FromUnixTimeMilliseconds(1310522400000).DateTime
Newtonsoft.Json.JsonConvert.SerializeObject(Convert.ToDateTime(dr[col.ColumnName])).Replace('"', ' ').Trim();