Mommies, did you give your kids vitamin D? From what month can it be g…

Mommies, did you give your kids vitamin D? From what month can it be given? Or is it necessary at all? We were told at the appointment that it's not necessarily required, just go for 8-10 hours in the open air. The street is terrible heat, we go early in the morning ?? If you do give it, which ones are good?