Kleinblatt is closed on those holidays (2021):

January 1st  New Years Day
March 27th to April 4th  Pessah (jewish easter)
May 17th  to May 18th Shavouoth (jewish pentecost)
July 24th to August 15th yearly holidays
September 7th till September 8th  Rosh hashana (jewish newyear)
September 16th  Yom kippoer (day of reconciliation)
September 21st to September 22nd      Soekoth (feast of tabernacles)
September 28th to September 29th  Simchat torah (feast of the bible)