The following Japanese National Holiday’s days are different in 2021 due to Tokyo Olympic Year.
Your 2021 calendar may be edited before the changes and indicating July 19 (Mon) as Marine Day, October 11 (Mon) as Sports Day and August 11 (Wed) as Mountain Day, however, all of which are not holidays anymore but normal working days now.
Please note and mind of these changes.
2021 Holidays in Japan from July towards the end year after the changes as follows.
July 19 (Mon) – No longer a holiday
July 22 (Thu) – Holiday (Marine Day)
July 23 (Fri) – Holiday (Sports Day)
Aug 8 (Sun) – Holiday (Mountain Day)
Aug 9 (Mon) – Substitute Holiday
Aug 11 (Wed) – No longer a holiday
Sep 20 (Mon) – Holiday (Respect-for-the-Aged Day)
Sep 23 (Thu) – Holiday (Autumnal Equinox Day)
Oct 11 (Mon) – No longer a holiday
Nov 3 (Wed) – Holiday (Culture Day)
Nov 23 (Tue) – Holiday (Labour Thanksgiving Day)
Those changes are applicable only for 2021 – Tokyo Olympic Year.