I am trying to show a section in my website with either 3 months or 1 month from the current month and this depending on the screen size. User can then loop through the differents other months with the arrows in the screen month by month. Till now it seems working correctly. However I am struggling finding why when reaching february = (fevrier here) month it is not correctly posted and instead it shows March (Mars here) even though the calendar show 28 or 29 days caracteristic of february. May somebody find the reason why and explain it please. below is a reproducible snippet.