C# Datetime时间指定时区

string start_time_str = "2018-03-21 06:00:00";

DateTime.Parse(start_time_str)
2018/3/21 06:00:00 1521612000 格林威治时间UTC

DateTime.Parse(start_time_str).ToLocalTime()
2018/3/21 14:00:00 1521612000  东八区时间EST


DateTime.SpecifyKind(DateTime.Parse(start_time_str), DateTimeKind.Local)
2018/3/21 06:00:00 1521583200  东八区时间EST