US companies report quarterly, and the bulk of the S&P 500 reports within a four-week window that starts a fortnight after each quarter ends. The large banks open it, and the mega-cap technology names in the middle weeks set the tone for the indices.
Prices respond to the gap against expectations, not to the results themselves. A company can grow profit thirty per cent and fall sharply because consensus expected thirty-five, which is why "beat" and "miss" are always measured against the estimate.
Guidance usually moves the stock more than the quarter does. The reported numbers describe a period already priced in; the outlook for the next one resets every forecast, and a strong quarter with weak guidance is a reliably poor combination.