Formula to calculate a year back at month end

[Declamatory]

Good day,

I have a date in column CN that shows the last business day in the month. So for February this is 2021-02-26.

I have to report for a year so need in column CM to show the start of the reporting period which would be the first day from a year ago in this case the resulting value would be 2020-03-01

Can somebody help we with a formula that would get that result but also update when future data is pasted into the sheet. So when I do March reporting the the value in CN would be 2021-03-31 and I would need the value in CM to be 2020-02-01

Thank you

 

[jasonb75]

Easiest way would be

=EOMONTH(A1,-12)+1

Where A1 contains the reference date.

So when I do March reporting the the value in CN would be 2021-03-31 and I would need the value in CM to be 2020-02-01

I've assumed that it should be 2020-04-01, not 2020-02-01?

 

[Declamatory]

Thanks so much.