string firsttime = "";

string secondtime = "";

DateTime firstDateTemp = DateTime.ParseExact(firsttime, "yyyyMMddHHmmss", new System.Globalization.CultureInfo("zh-CN", true));

DateTime secondDateTemp = DateTime.ParseExact(secondtime, "yyyyMMddHHmmss", new System.Globalization.CultureInfo("zh-CN", true));            

TimeSpan span = firstDateTemp.Subtract(secondDateTemp);

然后，如果相差一天，那么span.Days=，如果是一年，那么span.Days=<br>             span.Hours, span.Minutes就不举例了

DateTime onetime = DateTime.Parse("2014-2-26 05:32:22");

    DateTime twotime = DateTime.Parse("2014-2-26 05:31:22");

    TimeSpan span = onetime .Subtract(twotime );