Equivalent of SPRelativeDateTime.GetRelativeDateString in CSOM sharepoint 2013

What is the equvalent API for SPRelativeDateTime.GetRelativeDateString in sharepoint 2013 Client object model

using (SPSite site = new SPSite("http://your.site"))
{
    using (SPWeb web = site.OpenWeb())
    {

        DateTime DateInPast = new DateTime(2014, 4, 14, 18, 38, 0); 
        string DateString; 
        //the difference between DateTime.Now and file past are about 4 minutes
        DateString = SPRelativeDateTime.GetRelativeDateString(web, DateTime.Now, DateInPast); 
    } 
}