return the date that value

Mascarello 

alannavarro 's solution is broadly correct.  Using a different version of Excel, my solutions look somewhat different, but are broadly similar in approach

= BYROW(amount,
    LAMBDA(a,XLOOKUP(TRUE,ISNUMBER(a),date,""))
  )


= XLOOKUP(
    TRUE,
    ISNUMBER(INDEX(amount,@k,)),
    date,
    "")

What I have done, since you report that the >0 test does not work, is assume that the apparent blank cells in fact have text content.  The ISNUMBER function works in that situation, though a 0 would then cause a wrong result.