using System.Globalization;
using System.Reflection;
using System.Xml.Linq;
using System.Xml;
using System.Linq;
using System;
public class Program
{
public static void Main()
string xmlInput = @"
<root>
<element>
<timestamp time='2016-09-15T13:45:30'>
</timestamp>
</element>
<timestamp time='2016-10-16T13:45:30'>
</root>";
XDocument xdoc = XDocument.Parse(xmlInput);
xdoc.Descendants("root").Elements("element")
.Where(x => DateTime.Compare(DateTime.Parse(x.Element("timestamp").Attribute("time").Value,null, DateTimeStyles.RoundtripKind).Date, DateTime.Now.Date) !=0).ToList().ForEach(x => x.Remove());
Console.WriteLine(xdoc);
}