string str1 = "2017-2-13 23:59:59";
string str2 = "2017-2-14 0:00:01";
DateTime d1 = Convert.ToDateTime(str1);
DateTime d2 = Convert.ToDateTime(str2);
Console.WriteLine(d1.Date);
Console.WriteLine(DateTime.Now);//当前时间
Console.WriteLine(DateTime.Today);//0:0:0
TimeSpan sp = d2 - d1;
Console.WriteLine(sp.Days);//0
var sp2 = d2.Date - d1.Date;
Console.WriteLine(sp2.Days);//1
//DateTime.Today == DateTime.Now.Date;