This means that 67% of the gains since the market lows of October 2002 have come on the first trading day of the month. The last two months have been especially profitable, with June 1st going up 2.05% and July 3rd going up 0.79%.
It's that time of the month again - the first of the month. During this bull market, the cumulative return of the S&P 500 on the first trading day of each month is 27.04%. This blows away the cumulative return of the rest of the month which is just 13.44%.