Are You Ready?
We normally get a live (aka nearly dead) evergreen tree for a Christmas tree the first weekend in December.
We don't normally check out the strings of Christmas lights beforehand to see if they work. Most of the time they still do. After all, why shouldn't they? It's not like someone has been playing with them over the past ~11 months.
So it's good that there is a day like Non-Working String of Christmas Lights Preparedness Day on which you can get ready for the shock (not literal) of finding out that one (or...gasp...more) of your strings of lights don't work this year.
Note that you do not have to actually check the strings of lights today. You only have to prepare yourself for the possible eventuality.
How prepared you have to make yourself depends on how many strings of lights (and thus the probability that one has gone south) you have. The more strings, the more prepared.
Don't spend a whole lot of time on this.