Yes. A strike can be canceled, but they will not be able to willy-nilly change the date of a national strike from the 21st to the 20th. There is too much planning that goes into a nationwide strike. It may not happen on October 21st, but it definitely will not happen on October 20th, or any other time in October if it is canceled or postponed. They have to line up the mayor of practically every city in Italy to have nationwide strike.