So how did they hide ET for weeks?
From the opening of the film through the “ET phone home” stuff is four consecutive days. We can clearly see the moon in Elliot’s back yard and it is a crescent. Then suddenly we are at Halloween and we get the famous shot of the bike flying across a very full moon. That would suggest 7-10 days have passed during which ET is building his machine.
But how did they keep him hidden for that long?
https://www.reddit.com/r/movies/comments/jcofye/so_how_did_they_hide_et_for_weeks/