"This will have been a happy day!"
Winnie says this in Act One, Part Three. The tense she uses to describe the happiness of the day—the future perfect—is one that, in all practicality, does not exist: it is in the no-man's-land of the past of some future point, and never really arrives. The tense suggests that Winnie is suspended between the past and future. She has memories of her life before the mound, but they are incomplete, and her short-term memory also has holes. In an unchanging world, there is no distinction between past and present, so memory is not necessary. If something does not exist now, such as her breasts, then it never has, and it becomes an "empty word." Her only expectations for the future are her rituals, which are less a future but more a recurring, static present.