Easter egg Chapter 13?

In chapter 13 around listing 13.14 there’s a variable that seems like an Easter egg. It’s this line of code:
var bigCityPopulation = 4_061_981. The number sure seems like a birthday April 6th, 1981. Or it could also be Apri 7th, 1981 after the bigCityGrowBy(10_000) is applied.
Matt? John?