The union said its 115,000 members will strike in the run-up to Christmas, on December 9, 11, 14, 15, 23 and 24. This is in addition to strike dates around Black Friday and Cyber Monday (November 24, 25 and 30, and December 1), which were already announced.
Article source: https://www.huffingtonpost.co.uk/entry/why-are-royal-mail-workers-striking_uk_637749f2e4b0afce046d6e39