GMT时间转成时间戳
DateTime gtm = new DateTime(1970, 1, 1);
DateTime utc = DateTime.UtcNow.AddHours(8);
int timeStamp = Convert.ToInt32(((TimeSpan)utc.Subtract(gtm)).TotalSeconds);
时间戳转换成时间
int timeStamp = 1326332584;
DateTime d = ((new DateTime(1970,1,1))).AddHours(8);
d = d.AddSeconds(timeStamp );