2018
2018
[Megan is walking.] Megan: I wonder if 2018 will be a leap year.
[Now it turns out that Cueball walks behind Megan.] Cueball: ...it won't be, right? Megan: I doubt anyone knows at this point.
[Same scene in a frame-less panel.] Cueball: No, it's definitely not. Leap years are divisible by 4. Megan: Right, and for odd numbers, that's easy. Megan: But 2018 is even. Megan: 50/50 chance.
[Zoomed-out view with both walking in silhouette on a dark slightly curved ground.] Cueball: I can settle this with a calculator. Megan: No way. If it were easy to factor large numbers like that, modern cryptography would collapse. Cueball: I see. Megan: I just hope we manage to brute-force it by February.

In this, the first of two New Year comics in a row, Megan wonders whether 2018 will be a leap year . Cueball thinks 2018 will not be a leap year, and Megan responds that she "doubts anyone knows at this point." This appears to be a jab at people who suggest that anything they don't know is generally unknown. As Cueball says, leap years occur every four years (though there are a few exceptions - a year divisible by 100 is not a leap year, unless it is also  divisible by 400), adding an extra day to account for the fact that Earth takes a bit longer than 365 days to orbit the Sun. Therefore, most years that are a multiple of four are leap years. As Megan says, this is easy for odd-numbered years, since no odd numbers are divisible by four. However, for even-numbered years, it isn't quite as simple. (Though, since the number 2,000 is evenly divisible by 4, the problem can be reduced to the much simpler question of whether the number 18 is divisible by 4.)
The last panel expresses a misunderstanding of modern public-key cryptography , which relies on the fact that it is difficult to factorize large numbers. Megan is applying this concept to the year, claiming that it is hard to determine whether or not 2,018 is a multiple of four and hence is a leap year. In reality, factorization is not needed here, since we already know the factor in question, which is four. Megan states that, if it were possible to factor large numbers with a calculator, modern cryptography would collapse. While true, it is true only for truly large numbers (hundreds of digits), and no factorization is needed in this case.
At the end of the strip, Megan hopes the answer can be brute-forced by February. Brute force is a method of breaking cryptography by trying every possible option until one works. This is misdirection upon misdirection, in that, even if we needed to factorize 2,018 (which we don't), the simplest brute-forcing algorithm would need to try only 14 numbers -- each prime from 2 to 43 (the square root of 2,018 is closest to 44). In cryptography, the algorithms use numbers much, much bigger than 2,018 -- on the order of hundreds or even thousands of digits.
The title text refers to calculating which day Christmas will fall on. As Christmas always lands on December 25 by definition, the day of the week varies from year to year, though it's always the 359th or, in leap years, the 360th day of the year. Still, determining which day of the week December 25 lands on is not a difficult problem to solve, requiring only a few mathematical operations to compute. Alternatively, this might be an oblique reference to Easter, the date of which jumps from year to year according to a multi-layered algorithm that most people don't know. The changing date of Easter was recently included in 1930: Calendar Facts . Additionally, uncertainty with the regard to the date of Christmas has also been referenced in 679: Christmas Plans .
A handy coincidence to help with this problem for those living in America or following American politics is that leap years fall on presidential election years.
[Megan is walking.] Megan: I wonder if 2018 will be a leap year.
[Now it turns out that Cueball walks behind Megan.] Cueball: ...it won't be, right? Megan: I doubt anyone knows at this point.
[Same scene in a frame-less panel.] Cueball: No, it's definitely not. Leap years are divisible by 4. Megan: Right, and for odd numbers, that's easy. Megan: But 2018 is even. Megan: 50/50 chance.
[Zoomed-out view with both walking in silhouette on a dark slightly curved ground.] Cueball: I can settle this with a calculator. Megan: No way. If it were easy to factor large numbers like that, modern cryptography would collapse. Cueball: I see. Megan: I just hope we manage to brute-force it by February.
