Subtract days from a DateTime

I have the following code in my C# program.

DateTime dateForButton =  DateTime.Now;  
dateForButton = dateForButton.AddDays(-1);  // ERROR: un-representable DateTime

Whenever I run it, I get the following error:

The added or subtracted value results in an un-representable DateTime.
Parameter name: value

Iv'e never seen this error message before, and don't understand why I'm seeing it. From the answers Iv'e read so far, I'm lead to believe that I can use -1 in an add operation to subtract days, but as my question shows this is not the case for what I'm attempting to do.

DateTime dateForButton = DateTime.Now.AddDays(-1);

That error usually occurs when you try to subtract an interval from DateTime.MinValue or you want to add something to DateTime.MaxValue (or you try to instantiate a date outside this min-max interval). Are you sure you're not assigning MinValue somewhere?

You can do:

DateTime.Today.AddDays(-1)

You can use the following code:

dateForButton = dateForButton.Subtract(TimeSpan.FromDays(1));

The dateTime.AddDays(-1) does not subtract that one day from the dateTime reference. It will return a new instance, with that one day subtracted from the original reference.

DateTime dateTime = DateTime.Now;
DateTime otherDateTime = dateTime.AddDays(-1);