First of all, Chinese festivals correspond to dates on the Chinese lunar calendar. As a result, the festivals don't always fall on the same date on the Western Gregorian calendar. The Chinese New Year, for example, started on Jan 31 this year and on Feb 10 the year before.
The only major Chinese festival to fall on September or October is the
Mid-Autumn Festival. The Japanese equivalent is
Tsukimi. Neither festival has anything to do with the sea. Both, on the other hand, originated from autumn harvest festivals.
Fifty knots roughly equals 93kmh. The Senkaku Islands are about 1,885km away from Tokyo. You can do the maths from there.