Ryan Detrick of LPL Research sums it up: 

New all-time highs the first 4 days of year for the S&P 500 Index.

2 more up days and ties 1964 for longest streak of new highs to start a year.

3 more up days to tie 1987 for longest win streak to start a year.

1964 saw solid low double digit gains and 1987 saw fantastic gains first 8 months.