Question

I have an instance of DateTime that I get from my database, I want to subtract it from DateTime.Now and find out if 4 hours were passed. How do I do that?

Also when should i use DateTime.UTCNow or DateTimeOffset

Answer 1

You can use the subtraction operator to get a TimeSpan:

private static readonly TimeSpan MinimumTime = TimeSpan.FromHours(4);

...

if ((dateFromDatabase - DateTime.Now) > MinimumTime)
{
    ...
}

As for whether you need UTCNow or Now… it will depend on what happens to time zones when you fetch the data from the database. DateTime is not terribly clear on this front 🙁

If you can fetch the value as a DateTimeOffset to start with, then you can use DateTimeOffset.Now instead and it should be simpler to work out any time zone issues.