Coinstar
by Jeff
Image text: Plus they take like 9%.
This comic combines the holiday tradition of giving out and consuming chocolate coins, which are chocolate formed in the shape of coins with foil wrappers and the Coinstar vending machines that you see frequently in Grocery stores and shopping malls around the US. The Coinstar machines take all your coins, sort and count them and then give you the amount of money in cash (less 9 or 10% as it says in the image text - but if you get the Amazon gift card, you can keep the whole proceeds.)
Also, just as a reminder, we are still submitting entries for explanations of back catalog xkcd comics. We have got a bunch of awesome entries so far that I haven't had time to go post yet, so don't hesitate to submit!
Advent Calendar
by Jeff
Image text: I think you could get up to about 11:59:57 before you'd have trouble swallowing the chocolates fast enough. At that point, you'd need some kind of a liquify-and-chug apparatus to get up over the 11:59:59 barrier. Anyway, Merry Christmas!
This comic is about an Advent Calendar, which is a calendar for only the period of Advent, which is considered by the Christian calendar to be a month before Christmas. In a lot of traditions, this calendar has little doors with a piece of chocolate behind each door. Other people give very small presents on each day of Advent.
This Advent Calendar belongs to Zeno, who was a Greek philosopher who lived from ca. 490 - 430 BC. (So, obviously, he would not have had an Advent Calendar, as this tradition was not in place yet and according to the Christian calendar, Jesus was not even born yet!)
Zeno was the master of the dichotomy of motion. His dichotomy paradox indicated that something that is traveling in a direction, must arrive at the half-way point before it arrives at the destination. Since any finite destination can be divided in half (as seen in the Advent Calendar above) - the paradoxical conclusion then would be that travel over any finite distance can neither be completed nor begun, and so all motion must be an illusion.
So, if you are Zeno, your Advent Calendar means that it will never be Christmas, just smaller and smaller milliseconds until Christmas. Bummer!
Don't forget, we are soliciting help from you on filling out explanations for XKCD's back catalog. Perfect for something to do while you have time off around the Holidays!
Tradition
by Jeff
Image text: An 'American tradition' is anything that happened to a baby boomer twice.
This comic uses the source of the American Society of Composers, Authors and Publishers to say that the 20 most played Christmas songs in the US between 2000 and 2009 were all released between the 1930s and 1970s. I'd love to see this research, because the most popular Christmas album of all time was not released until 1994, "Merry Christmas" by Mariah Carey. This album featured what I consider to be the most ubiquitous song around this time of the year which is "All I Want For Christmas Is You" which is also featured prominently in the very popular (and frequently replayed) movie Love Actually from 2003. The song is the only holiday song and ringtone to reach multi-platinum status in the U.S. So, I usually don't take a look at the information that Randall presents to us and think it is incorrect, but this one just seemed egregious based on the popular success of a mid-90s release.
(Christmas is December 25th, for any Americans who have been living under a rock for the past 2 weeks or so and don't own a TV and are somehow able to escape the crushing commercialism of the Christmas season. And "this time of the year" is apparently considered Christmas time despite the fact that not everyone celebrates Christmas in the US and in the world).
Caroling
by Jeff
Image text: For a thousand generations we vowed never to forget how his soldiers feasted on our brother Stephen.
Here are the lyrics for the first part of the Christmas Carol, "Good King Wenceslas"
Good King Wenceslas looked out, on the Feast of Stephen,
When the snow lay round about, deep and crisp and even;
Brightly shone the moon that night, tho' the frost was cruel,
When a poor man came in sight, gath'ring winter fuel.
First and foremost, Wenceslas was not a king, but merely a duke. The "kingship" was given to him ceremonially after his death. Secondly, the Wenceslas that the carol is about did not massacre any people and I'm sure that this is Black Hat merely playing a prank on unsuspecting innocent carolers. (As an aside, does anyone "carol" at random people's houses anymore? Seems like an antiquated notion. Plus, who wants people singing loudly in front of their house?)
The image text references "the Feast of Stephen" which is also known as the "Feast of St. Stephen" or "St. Stephen's Day", which is a holiday celebrated on the 26th or 27th of December, depending on the Western or Eastern church respectively. It is not actually a feast of a person named Stephen, instead a celebration of the Saint.
Incident
by Jeff
Image text: He sees you when you're sleeping, he knows when you're awake, he's copied on /var/spool/mail/root, so be good for goodness' sake.
This comic, fittingly posted on Christmas Eve in the United States. Christmas being a Christian holiday celebrating the birth of Christ on December 25th. (Didn't know how granular I should be. I'm sure there are some people who haven't heard of Christmas if they have lived under a rock for their entire life. If so, I'd like to say "Hi, and welcome to the internet.")
In this comic, Cueball is on a Linux computer tried to change his user account from his normal access to the access of a super user by using the command "sudo". Sudo is a famous phrase in xkcd lore, made famous by comic 149. When Cueball is unable to use "sudo" because his account is not authorized, the system says that the incident has been logged.
In the comic, sudo and the system report the incidents to Santa Claus, who in Christmas lore makes a list of who is naughty and who is nice. If you are nice, you get presents, if you are naughy, you get a lump of coal. When sudo reports to Santa that Cueball's account is not authorized, he puts Cueball on the naughty list.
In the image text, which is a parody of the famous Christmas song, "Santa Claus Is Coming To Town", /var, /spool, /mail, /root are all folders in a Linux file system.
Tree
by Jeff
Image text: Not only is that terrible in general, but you just KNOW Billy's going to open the root present first, and then everyone will have to wait while the heap is rebuilt.
A heap is a computer science data structure in which if B is a child node of A, then key(A) ≥ key(B). In the case of this xkcd comic, that means that the greatest present will be on top of the heap also known at the root present. In the image text, Billy picks the root present, which causes the heap to be rebuilt which means that a new present will take the place at the top of the heap.