Do the number of days in a month affect monthly return? (seasonality) When I see data like monthly return on news or tv, I always find the concept a bit strange, because obviously if you calculate monthly return for February and March, all things being equal, the monthly return of March would be slightly larger than February due to the fact March has more days than February. Is this the case in real life?
Let's make a fake example.

Compound interest of 0.1% over 30 days gives

$$1.001^{30} = 1.030439088$$

Compound interest of 0.1% over 31 days is

$$1.001^{31} = 1.031469527$$

And the percentage change is 1.000970497. That is, you would over estimate the growth rate of a stock by 0.009% if you would compare 30days and 31days without adjusting for it.