//把UTC时间转换成北京时间
DateTime now = DateTime.Parse(DateTime.UtcNow.ToString(), new CultureInfo("zh-CN"), System.Globalization.DateTimeStyles.AssumeUniversal);
//把北京时间转换成UTC时间
DateTime nowUTC = now.ToUniversalTime();
原文：http://www.cnblogs.com/lidaying5/p/4494166.html