When can I apply through the weighted lottery?
Each year’s main lottery will be held in February of the previous year. For instance, for the first few weeks of February 2018 applications were accepted for the 2019 Main Lottery.
This is from:
National Park Service
U.S. Department of Interior
Grand Canyon National Park
River Permits Office
last updated June 5, 2018 (from a pdf on their site)
I don't get mad, I get even.