[krastanov]

On the contrary, it is a pretty fundamental assumption in all of our fundamental theories (with some bows and whistles).

A point of confusion might be that the surroundings of the experiment might influence it and the surroundings would depend on whether it is a workday or a weekend, etc. But this is a bad experiment. The correct interpretation is "if my experiment is isolated so that external events do not influence it (like all good experiments), then I will get the same results no matter whether I do it today or wait until tomorrow". Another way to phrase it is "there is no dependence on the variable 't' in the fundamental laws".