How many days until…

Time is a fun and challenging technical problem to solve, and most recently I had to answer the question: how many days is it until Christmas?This post is an over the top deep dive into the complexities of accurately answering a question, which boils down to: a ball of wibbly wobbly… time-y wimey… stuff.
Christmas religious (or commercial!) feelings aside, this question, although simple from one human to another, when broken down has lots of complicated moving parts.
I had made a LaMetric countdown to Christmas that displayed the number of days to Christmas, which worked for me, but with all software, didn’t work completely right all of the time.