This market will resolve to "Up" if the official S&P 500 Index open price for S&P 500 (SPX) on June 15 is higher than the official S&P 500 Index closing price for SPX on the most recent prior trading day.
This market will resolve to "Down" if the official S&P 500 Index open price for S&P 500 (SPX) on June 15 is lower than the official S&P 500 Index closing price for SPX on the most recent prior trading day.
E.g., ordinarily, a market on Monday would refer to the previous Friday for its most recent closing price, unless that Friday were a market holiday, in which case it would refer to Thursday, or the next most recent trading day.
If the two prices are exactly equal, this market will resolve 50-50. Note that all figures will be rounded to the nearest cent using standard rounding.
If SPX does not trade at all during the regular session, the market will resolve 50-50.
If either of the relevant days are shortened (for example, due to a market holiday schedule), the official open/close price published by S&P 500 Index for that shortened session will still be used for resolution.
If the previous trading day has no official closing price (for example, due to a trading halt into the market close, system issue, delisting, or other disruption), the market will use the last valid on-exchange trade price of the regular session as the effective closing price.
The resolution source for this market is the Wall Street Journal, specifically the Open/Close values published by the WSJ under "Historical Prices".
US:
https://www.wsj.com/market-data/stocks
EMEA:
https://www.wsj.com/market-data/stocks/emea
ASIA:
https://www.wsj.com/market-data/stocks/asia