SPO Calculated Field issues

Hi,

I have a relatively simple list which includes a date-time field - Published

I wish to group by the year-month in the format "yyyy-mm" by creating a calculated field.

However, the closest I can get is >>>=""&YEAR(Published)&"-"&"0"&MONTH(Published)<<< which obviously only works for months 1 thru 9.

All my attempts to use, TEXT, RIGHT, or IF with LEN are unsuccessful. I can retrieve the result of LEN but cannot seem to get any further ...

Even trying to get the first day of the month is failing >>>=DATE(YEAR([Published]),MONTH([Published]),1)<<<

So, if anyone can provide a formula to produce "yyyy-mm" from a date column, I would be very grateful

Yours,

hugmys0ul