In the computer-programming field we often create tables with dates which serve more or less as calendars for our programs. Then we populate these tables with dates, something like the following:
Date | Business_Day_Indicator |
1/1/2012 | N |
1/2/2012 | N |
1/3/2012 | Y |
1/4/2012 | Y |
But we don't want to spend the rest of our lives populating such a table to infinity, so we take a reasonable guess as to how long the program will be used, and we populate the table up to that date. For example, one such table was populated up until 12/31/2020.
Now for the point of all this: if some primitive, superstitious, ignorant culture were to find this calendar and conclude that 12/31/2020 must be the end of the world, we would have the same situation we see with those who think that because the Myan calendar was finite the world will end at the same abitrary date that they chose to stop populating their calendar.