The day of the week test is one we often use to see if the catalog is any good.
Mine blasts tend to be during the week, and some often slip by the analysts compiling the catalog, for example.
When the full staff is at work, there is a tendency for fewer events to me missed, as well.
Day/night tests are also common, again with the idea that any differences are most likely due either to the habits of the people monitoring or differences in the noise level (like wind) between the day and the night.

John