I can't think of an alternative to what you have other than putting your year, month, day and minute into a variables and then comparing them. The statement you have isn't too bad. I would say go ahead and use it.
As for your second question. To subtract 10 minutes, there is no subtract method. Fortunately, there are AddYears, AddMonths, AddHours, etc.
You should be able to just do Addminutes(-10). Example:
date.AddMinutes(-10); //Subtracts 10 minutes
That's the way it's done in my book. That's how I remember it
