User-defined named dates with logical expressions

There is currently no way to add custom user-defined named dates with advanced logic. For example, I wish to create a task to complete my taxes before Tax Day in the United States, and I want this task to be recurring. Though Tax Day is typically April 15, there are several edge cases when Tax Day may fall on a different day. I want to have the due date changed based on a logical expression for each recurrence. In non-programmatic language:

- If April 15 falls on a Monday, Tuesday, Wednesday, or Thursday, set due date to April 15
- If April 15 falls on a Friday or Saturday, set due date to April 18
- If April 15 falls on a Sunday, set due date to April 17

In this case, if I have my task set to recur yearly, then Tax Day in 2012 would have a due date of Tuesday, April 17, 2012 and the following year's recurrence would have a due date of Monday, April 15, 2013.