If it remains somewhat unclear whether we have actually gotten beyond postmodernism yet, nothing could be clearer than that we have left its peak years behind us, presumably somewhere in the Seventies and Eighties, and its onset (whenever that was) even farther back. Enough time has elapsed for us to be able to discern more of the internal articulation of the era--its successive moments or phases. Initially, the tendency was to view postmodernism either as break, sharply profiled against the preceding modernist era (e.g., McHale, Postmodernist), or as single monolithic moment, consistent across its entire span, reflecting the logic of particular world-historical phase (e.g., Jameson, Postmodernism). Looking back from our twenty-first-century perspective, it is easier to grasp what Jameson calls the dialectic of the break and the in late-twentieth-century cultural historiography. There is, Jameson says, a twofold movement in which the foregrounding of continuities, the insistent and unwavering focus on the seamless passage from past to present, slowly turns into consciousness of radical break; while at the same time the enforced attention to break gradually turns the latter into period in its own right (Singular 24; see Wegner 20). Bring enough reflective pressure to bear on period, and it begins to look like break; squint intently enough at break, and it begins to look like period. Squinting hard, then, at the postmodern break or moment, what kind of internal temporality begins to come into focus? How might we begin to distinguish sub-periods and locate internal thresholds, constituent moments within the postmodern moment? It is in the nature of the periodizing enterprise that every gesture of temporal delimitation is kind of thought experiment or enabling fiction, necessarily arbitrary, though not for that reason inconsequential. the contrary, every such decision has knock-on consequences for the kind of period or sub-period one constructs and the kind of cultural-historical narrative one tells: choose particular onset date or threshold moment, and particular continuities and discontinuities, causes and effects, themes and figures, leap into focus, while others recede into the background; choose different date, and different continuities, discontinuities, etc., emerge. Suppose we ask, when did postmodernism begin? Onset Though earlier dates have sometimes been advanced, consensus view might be that postmodernism can be dated to the long Sixties, spanning the years from the late Fifties to the early Seventies (see, e.g., DeKoven). Particular years have been proposed, more or less seriously, in the spirit of Virginia Woolf's On or about December, 1910 1958, advanced by the Fluxus artist Dick Higgins as the onset of what he called postcognitive art, once seemed compelling to me, but now seems too early, reflecting not postmodernism's onset so much as the achievement of critical mass by certain postwar avant-garde (Black Mountain, the New American Poetry, Higgins's own Fluxus circle, etc.; see Belgrad; Miller). 1973, favored by Jameson and extensively documented by Andreas Killen, seems to me too late; it correlates, I would rather say, with the relaunch of postmodernism, its consolidation and the onset of its peak period (see below). Roughly splitting the difference, I once ventured the thought-experiment of dating postmodernism's onset to the year 1966, and ended up convincing myself of that year's plausibility as candidate. Other years (1967, 1968) no doubt have stronger claim to attention in world-historical terms, but its relative lack of landmark events actually strengthens 1966's appeal, (1) making it test-case for the hypothesis that movements in culture are not necessarily in synch with world-historical epochs, that asynchronicity, slippage, and semi-autonomy prevail across the different partial histories that make up capital-H History. …