In MacrosFirst you have the ability to copy individual meals or entire days to another day.
Tap the ...
button next to the meal name
Tap Copy To Date to copy this meal to another date or Copy From Date to copy a meal from a different date into this meal.
Select the Date and Meal into which you want to copy to or from.
Note: Copying a meal into another meal adds to, but does not replace, the contents of the meal.
Tap the ...
button in the top right corner of the daily log
Tap "Copy Today's Meals"
Select the Date into which you want to copy today's meals.
Note: Copying a whole day's meals will completely overwrite and replace whatever meals and foods may already exist on the date that you're copying into.