How do weekends/holidays affect deadlines for past years?

Question

What happens with weekends and holidays and amended tax deadlines? Take for instance a 2014 amendment.

2014 taxes were due on April 15, 2015.

The statute of limitations for amending taxes is 3 years past the due date. 3 years would be April 15, 2018.

However, April 15, 2018 is a Sunday.

Even more, April 16, 2018 is Emancipation Day, the District of Columbia's holiday that's completely unrelated to taxes (seriously, that's when Lincoln signed the Emancipation Proclamation. In DC.) That makes the deadline for 2017 taxes April 17, 2018.

What do these weekends and holidays do, if anything, to the "statute of limitations" deadlines for filing or amending past years (2014 in this example)?

Answer 1

The IRS site states the last chance to claim a refund for a 2014 tax return is April 17, 2018.

This seems consistent for prior years, rather than being 3-years exactly, it's the current year tax deadline.

Last chance for 2014 - Tuesday, April 17, 2018
- Original 2014 tax deadline was Wednesday, April 15, 2015
Last chance for 2013 - Tuesday, April 18, 2017
- Original 2013 tax deadline was Tuesday, April 15, 2014
Last chance for 2012 - Monday, April 18, 2016
- Original 2012 tax deadline was Monday, April 15, 2013

Those are the only years I see on IRS site. Those all work to benefit the late-filer, so tried to find a year when the original tax deadline was later than the 15th. In 2006 the original deadline was April 17th, 2007, according to RapidTax.com Thursday, April 15, 2010 was the last chance to claim a 2006 refund. I suspect that site is correct and that the IRS doesn't want to fuss with multiple due dates, so people get 3-years +/- a couple days.