I have almost no idea what to do with this observation, but I think there's a point of disanalogy between geometric and temporal continua, even if we take geometric continua to be 'directional'. Take a geometrical line from A to B. Here, we have a pair of limits and the extension between them. Now take a temporal continuum. But let's understand the temporal continuum as the time of some particular change. So a block of wood bleaches in the sun, going from dark to pale. The temporal continuum we're concerned with is the time that this change takes (say, one week). So suppose this temporal continuum also has two limits, C (at the beginning) and D (at the end of the change), and an extension between them. Geometrical continua needn't actually have minima and maxima, the 'line on a paper' is a case where they do. If this is so, then geometrical and temporal continua are in this sense analogous. But there's a problem with the idea that temporal continua have a minimum. Suppose C is an indivisible moment. Has any change been accomplished at C? If yes, then given that no change can be accomplished in a moment (since there is no temporal difference), there must be previous moment at which some change had been accomplished, and therefore C is not early enough to be the first moment of the change. If no change has been accomplished at C, then C is too early to be the first moment: it is not properly called part of the time of the change. So no matter what, the moment C cannot be the first moment of change. Nothing prevents us from having a last moment, but temporal continua (so long as they are considered the time of some particular change) cannot have a first moment. Temporal continua can have greatest lower bounds, but no actual minimum.

If I make a model of you using some lines on paper, I don't get to say that fundamentally you are just lines on paper, but that "inside the model" you're a real person. For the same reason, just because you can make a diagram of time that is not "made of time", doesn't mean you can say that the universe itself is timeless. In an early paper, Max Tegmark struggles to define his concept of possible worlds. He starts out by defining "formal systems" (page 5). There's lots of talk about letters, strings, rules. So wait, is he going to say that reality is made of letters? Well, no, he manages on the next page to get as far as talking about equivalence classes of formal systems, and then saying "When we speak of a mathematical structure, we will mean such an equivalence class, i.e., that structure which is independent of our way of describing it." This is still rather confused - he equates a mathematical structure with the set of all formal systems which describe the mathematical structure. So possible worlds still seem to be based in manipulations of letters, but now the possible world is something that mysteriously and platonically inhabits a manipulation of letters (and other letter-manipulations in the same class). The point is that for certain topics, the conceptual and notational system for reasoning about X tends to be substituted for X itself. Possible worlds are identified with formal systems that represent them, and time is identified with a sequence of imaginary arrows. I think the reason for the substitution is obvious: the properties of the representation are less elusive and easier to talk about, than the properties of the reality that they represent. It's easier to talk about rules for rewriting a string of symbols, or about chains of little arrows, than it is to talk about possibility and change.