It starts when CP begins staying open until at least 10PM daily - that day this year is June 8. The park usually closes before 10PM prior to June 8 (except weekends). A laser show can't be seen when it's not dark. I was there a week ago and did not get to see this, as the park was closing at 8PM. It was still light out at 9PM, one hour after close. I guess the light show on MF was a reasonable substitute, especially since it was visible from our room at Breakers!
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First we Rock - then we Roll!