User blog comment:Servant of Evillious/The Muzzle of Nemesis Booklet/@comment-149.160.226.79-20150428181701/@comment-6986530-20150428211725

In fact, the numbers are negative ones when you do the subtraction. We know that the Third Period can't be much older than 1500 years, so this is either an indication that they take place in earlier Periods (BTS being Second and Watching Us being First, for example) or that these negative numbers stand out from the rest of the dates because they're meaningless.

There's no way to be sure from this alone that the two are Evillious songs with a proper place in canon.