Editing 3019: Advent Calendar Advent Calendar

{{comic
| number    = 3019
| date      = December 2, 2024
| title     = Advent Calendar Advent Calendar
| image     = advent_calendar_advent_calendar_2x.png
| imagesize = 482x324px
| noexpand  = true
| titletext = The growth rate of items per day may may seem absurd, but it's actually much less than the acceleration in the 12 Days of Christmas song.
}}

==Explanation==
{{incomplete|Created by 4 ENVELOPE BACKS 3 NERDS A-EDITING, 2 TURTLE BOTS, AND A FUNNY NEW XKCD - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
Advent calendars are a form of countdown to Christmas consisting of a card or structure with one closed "window"/opening for each day. Every day, another "window" is opened (e.g. a cardboard flap is opened along perforations), revealing a small present (traditionally, just a thematic picture or chocolate). While the religious season of {{w|Advent}} traditionally begins four Sundays before Christmas, most Advent calendars begin on December 1st for simplicity. Notice that in 2024, when this comic was published, the Advent season coincidentally starts on December 1st.

In this comic, Randall has devised an Advent calendar that contains multiple smaller Advent calendars, each of which contains the same number of items as there are days left until (and ''including'') Christmas Day. By the time he reaches Christmas, he will have 325 different items, or 350 if counting the sub-calendars. The calendar is shown as it might be on December 2<sup>nd</sup>, the date of publication of this strip. The "window" for December 1<sup>st</sup>, in the upper left, has 25 sub-windows, of which 2 are open. (One was opened on December 1<sup>st</sup> and the other on the 2<sup>nd</sup>.) The "window" for December 2<sup>nd</sup>, 5<sup>th</sup> from the left in the bottom row, has 24 sub-windows, of which 1 is open.

It is not clear what is inside each sub-calendar. The usual filling would be chocolate, however it could also be possible that the advent calender advent calendars had even more advent calendars within.

The title text refers to {{w|The_Twelve_Days_of_Christmas_(song)|The Twelve Days of Christmas}}, a traditional Christmas carol in which the singer receives many gifts from their paramour for each day of the Twelve Days of Christmas. On day one, they receive one gift, and on day ''n'', they receive again all the gifts they received on day ''n-1'', plus ''n'' copies of a new gift. The exact gifts given each day vary by version of the song, receiving 78 gifts on day 12, for a total of 364 gifts. For the Advent calendar Advent calendar, each day a number of items equal to the number of days left until christmas are added. There are 364 items total in the 12 Days of Christmas, the final day itself having exceeded the gifts of the nested calendars (the sub-gift count being 325, and regardless of the 25 calendars also being included).

The advent calendar's advent calendar gift total follows the {{w|triangular number}} sequence of all new gifts on a given day being one more than those the day before: on the first day, this is 1 (the first sub-gift of the first sub-calendar); on the second, we now have 3 (add two sub-gifts from two sub-calendars); on the third, we have 6 (three sub-gifts added), etc. The formula for for the total on day ''n'' is <table style="display: inline-table; line-height: 0.6em; vertical-align: middle; font-size:9pt; text-size-adjust: none;"><tr><td style="text-decoration: underline">''n''(''n''+1)</td></tr><tr><td style="text-align: center">2</td></tr></table>. For the Twelve Days song (which goes from the 25th of December to 5th of January), ''each day'' adds to the total the next ''triangular number'' in the sequence: +1=1, +3=4, +6=10, etc... The formula for this {{w|tetrahedral number}} (a 'pyramid of triangular numbers') is <table style="display: inline-table; line-height: 0.6em; vertical-align: middle; font-size:9pt; text-size-adjust: none;"><tr><td style="text-decoration: underline">''n''(''n''+1)(''n''+2)</td></tr><tr><td style="text-align: center">6</td></tr></table>. This already starts in a more rapid escalation of gift-giving, immediately after the first day where both counts are at one item. However, due to the later start of the Twelve Days, one would have to extend the gift-giving patterns to the 17th Day Of Christmas (and thus the 41st day of Advent) for the number of ''true love'' gifts (969) to properly overtake the continuing meta-calendar's ones, with (902) or without (861) counting the sub-calendars as gifts.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[On a grey board, there are 23 Advent calendars behind large "windows", numbered from 3 to 25, plus two open calendars with their covers torn off.]
:[Each calendar numbered ''n'' has 26−''n'' squares in it.]
:[One open calendar has 25 squares, 2 of which are black. The other open calendar has 24 squares, one of which is black.]

:[Caption below the panel:]
:I like Advent calendars, so I got an Advent calendar that gives me a new one every day until Christmas.

{{comic discussion}}

[[Category:Christmas]]
[[Category:Calendar]]
[[Category:Songs]]