Like it says on the tin. My personal impression right now is that:

- during most of the 1920s, "the twenties" or "the '20s" meant the present decade
- during the 2020s so far, "the twenties" or "the '20s" has still meant the 1920s

If it becomes clear to me (or, in my absence, the mods) that "the twenties"/"the '20s" in contemporary popular discourse and/or journalism now means the 2020s, this will resolve to the year in which that happens.

Resolution criteria: if in 2024 Google searches for "the '20s" showed "the 2020s" instead of "the 1920s" in the knowledge panel, or there was no knowledge panel but "the 2020s" ranked higher in search results than "the 1920s", that would resolve it for me. In later years, Google or the knowledge panel may be considered less reliable; in that case I would resolve based on criteria like the consensus of experts, media style guides, and the like, hopefully as expressed in an uncontroversial, well-cited statement in a Wikipedia page.