C# DateTime to UTC Time without changing the time

问题:

How would I convert a preexisting datetime to UTC time without changing the actual time.

Example:

DateTime dateTime = GetSomeDateTime(); // dateTime here is 3pm
dateTime.ToUtcDateTime() // datetime should still be 3pm

回答1:

6/1/2011 4:08:40 PM Local
6/1/2011 4:08:40 PM Utc

from

DateTime dt = DateTime.Now;            
Console.WriteLine("{0} {1}", dt, dt.Kind);
DateTime ut = DateTime.SpecifyKind(dt, DateTimeKind.Utc);
Console.WriteLine("{0} {1}", ut, ut.Kind);

回答2:

Use the DateTime.SpecifyKind static method.

Creates a new DateTime object that has the same number of ticks as the specified DateTime, but is designated as either local time, Coordinated Universal Time (UTC), or neither, as indicated by the specified DateTimeKind value.

Example:

DateTime dateTime = DateTime.Now;
DateTime other = DateTime.SpecifyKind(dateTime, DateTimeKind.Utc);

Console.WriteLine(dateTime + " " + dateTime.Kind); // 6/1/2011 4:14:54 PM Local
Console.WriteLine(other + " " + other.Kind);       // 6/1/2011 4:14:54 PM Utc

回答3:

You can use the overloaded constructor of DateTime:

DateTime utcDateTime = new DateTime(dateTime.Year, dateTime.Month, dateTime.Day, dateTime.Hour, dateTime.Minute, dateTime.Second, DateTimeKind.Utc);

回答4:

Use the DateTime.ToUniversalTime method.