Hi @lava890 ,
It does look like there is something wrong with the formula.
I don’t fully understand all the parts of the formula, but in order to make it output 1 week (or 7 days) earlier, I added a minus 7 to get the date 1 week earlier.
Here’s my revised formula:
=arrayformula(if(row($A1:$A)=1,"Week", iferror(DATE(YEAR($A1:$A), 1, -3 + 7 * WEEKNUM($A1:$A) - WEEKDAY(DATE(YEAR($A1:$A), 1, 4), 1) + 1)-7)))
Note the -7 near the end.
This revised formula might not be the cleanest way to solve the problem, but it seems to work in my testing. Does it work for you?