No it hasn't have anything to do with our calendar or seconds or whatever, but with the seconds that were used before 1950 or something like that.
Before 1950 the defenition of a second was based on the length of a day. One revolution of the earth around its axis. The time it takes for the earth to complete one of these revolutions is not constant.
And don't come with the so-called argument that seconds are based on a year instead of a day, because for 1950 this was not the case.
I believe I read a post by your husband where he states that the speed of light is constant, but much higher then measured today because of something vague with light interacting with non-existing particles.