A cleaner version of the same code might look something like this;

s = GetTokenValue("RetrieveFieldValues_Birthdate").ToString();
if (!string.IsNullOrEmpty(s)) {
	contact.Birthdate = Convert.ToDateTime(s);
}

awesome, thanks. Ill give it a try and see what happens. 

Dang, no-luck. Its still not updating that field. I even tried both of your codes. You have any other ideas? Is there a way to to find out what exactly could be the issue? Like a debug error code or something. I have posted on the Salesforce boards but they are not as responsive as here. Thanks for the help. 

Are we confident the issue is in this section of the code?  How about hard-coding a good DateTime value like DateTime.Today  (Skip the If section and just use this line of code.  It should write today's date into the contact.Birthdate field)

            contact.Birthdate = DateTime.Today;

OK, Ill try that, because I'm not confident where the issue is at all. I'm jumping on to this project and writing code is not my strong suit. Thank for the help. 

Well adding that in there also did not add a date. I wonder if it could be the formatting of the metadata or if its the script. just seams weird that all these fields are moving over fine, just not the date. What else could we try?

So my guess at this point is that the value that we are assigning to the contact.Birthdate property is not what it is expecting.  Perhaps because we are passing it a datetime value and it is looking for a date only value?  Can you verify what type of data the Birthdate property is expecting?

That's kinda what I was thinking. I have this tool called data loader. The guy that was working on this showed it to me as a way to find out what the field names are. The customer has a couple of custom fields that I needed to check the naming on. The input value for birthday just date. 

The field in Laserfiche is a date field. I can try to change it to text and see what it does. 

This is a long shot but how about hard coding a 'date only' string and seeing if the API will convert that to a date only?

contact.Birthdate = "01/29/2016";

Workflow give me this when i tried that;

Error    1    Cannot implicitly convert type 'string' to 'System.DateTime?'    \Script2\Script 1.cs    90    33    Incoming Intake Forms - Update SF
 

Can you share the section of code where the contact object is being instantiated?

 //Change the binding to the new endpoint
           SfdcBinding.Url = CurrentLoginResult.serverUrl;

            //Create a new session header object and set the session id to that returned by the login
           SfdcBinding.SessionHeaderValue = new SessionHeader();
           SfdcBinding.SessionHeaderValue.sessionId = CurrentLoginResult.sessionId;

            Contact contact = new Contact();

            contact.Id = "";

            //string
            string s = null;

            s = GetTokenValue("RetrieveFieldValues_First Name").ToString();
            if (string.IsNullOrEmpty(s) == false)
            {
            contact.FirstName = s;
            }
            s = GetTokenValue("RetrieveFieldValues_Middle Name").ToString();
            if (string.IsNullOrEmpty(s) == false)
            {
            contact.Middle_Name__c = s;
            }
            s = GetTokenValue("RetrieveFieldValues_Last Name").ToString();
            if (string.IsNullOrEmpty(s) == false)
            {
            contact.LastName = s;
            }

            s = GetTokenValue("RetrieveFieldValues_Birthdate").ToString();
            if (string.IsNullOrEmpty(s) == false)
            {
            string date = s;
            DateTime dt = Convert.ToDateTime(date);
            contact.Birthdate = dt;
            }