What's your niche?
Better go with based on your current traffic ofmyour blog and page
Theoritical answer will be
Blog post: on the starting business day of the week depends on your country
SM post: if Saturday and Sunday is business holiday means I would schdule 2 to post friday and Saturday evening. Monday and Wednesday morning for the remaining two post
There’s no specific day but avoid mondays and sundays rest days are fine