From the Ishiuchi Maruyama News page:
Thank you very much for frequenting Ishiuchi Maruyama.
Please find the planned winter operation schedule for the 2017 Season below.
Wednesday December 21st 2016
※December 21 & 22 are the first ski days of season so adult lift tickets will be 3,100 yen, or 2,100 yen for junior and senior concessions. December 23rd to March 20th will be normal pricing.
≪Three Mountain Area Link Operation [across to GALA Yuzawa]≫
From Saturday January 14th to Monday March 20th
≪Night Skiing Operation≫
Friday December 23rd to Sunday March 19th
≪Spring Ski Pricing≫
Tuesday March 21st to Sunday April 2nd
※Adult lift tickets will be 3,100 yen, or 2,100 yen for junior and senior concessions
≪Planned Closing Day≫
Sunday April 2nd
※Snow conditions could cause changes to the schedule above.
Should changes occur we will post the news on our website, so please keep informed.