Formula to find the header index of the first non blank cell of a range in Excel?

Question

I have this table, which can be seen as a basic custom gantt chart:

And I would like to fill the A column with start dates, based on the first filled cell of the range on the same row, and the header value of its respective column (row 1). It's easier to show my expected result than write it actually:

Thanks very much for your help!

Answer 1

In A2 try this formula copied down

=IF(COUNTA(B2:Z2),INDEX(B$1:Z$1,MATCH(TRUE,INDEX(B2:Z2<>"",0),0)),"")

you may have to format column A with the required date format

assumes data up to column Z, adjust as required