TimeStamp.Text = BlogComment.Date.UtcNow.ToString("yyyy-MM-ddTHH:mm:ss.fffffffzzz");

@"yyyy-MM-ddTHH:mm:ss.fffffffzzz"

TimeStamp.Text = BlogComment.Date.ToString(@"yyyy-MM-ddTHH:mm:ss.fffffffzzz");

TimeStamp.Text = BlogComment.Date
                            .ToUniversalTime()
                            .ToString(@"yyyy-MM-ddTHH:mm:ss.fffffffzzz");

TimeStamp.Text =  BlogComment.Date.ToUniversalTime().ToString(@"yyyy-MM-ddTHH:mm:ss.fffffffzzz");

Stamp.Text = BlogComment.Date.ToString("yyyy-MM-ddTHH\:mm\:ss.fffffffzzz");

Stamp.Text = DateTime.UtcNow.ToString(@"yyyy-MM-ddTHH:mm:ss.fffffffzzz");

Stamp.Text = BlogComment.Date.ToUniversalTime().ToString(@"yyyy-MM-ddTHH:mm:ss.fffffffzzz");

string time = DateTime.UtcNow.ToString(
    "yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'fffffffzzz",
    DateTimeFormatInfo.InvariantInfo);