Solar sweeps are used as a measurement of time on Alternia. They are likely the troll term for years. Each solar sweep lasts 26 Earth months (or about 2.16 (repeating) Earth years), meaning six solar sweeps are exactly equal to 13 Earth years, putting the trolls at roughly the same age as the Kids.
To convert any number of years to sweeps, use the equation , where Y is Earth years and S is Alternian solar sweeps.
To convert any number of sweeps to years, use the equation .
A perigee is the moment a body orbiting Alternia is closest to it and is possibly the equivalent to an Earth month. Since all perigees mentioned thus far are "bilunar," it seems Alternia's two moons have identical orbits. There seem to be at least twenty-four perigees in a solar sweep, since Karkat's wriggling day occurs on "the 12th bilunar perigee of the 6th dark season's equinox", and there ought to be two equinoxes per solar sweep.
So far only two types of seasons have been mentioned and it is unknown how many other types of seasons, if any, there are.
- Dark seasons: there are at at least six dark seasons in a solar sweep, during which it The events of Hivebent take place during the dark seasons. It is unknown what or how many other types of seasons there are.
- Dim seasons: there are at least two dim seasons in a solar sweep. The page of Mindfang's journal Vriska reads is dated as the 14th bilunar perigree of the 2nd dim season's equinox.
One of Alternia's equinoxes occurs during the sixth dark season. Assuming full parallelism, this suggests that the other should occur during a sixth dim season. It seems that perigees can be counted between equinoxes as well as within a sweep.
The trolls never use the word "month" except when communicating with the kids, and even then possibly without understanding what it means. They make frequent use of "day" and "week," although notably days are never numbered, not even with respect to perigees. Trollian measures time in hours, as does Karkat when recapping their Sgrub session as having lasted roughly 600 hours, but this may be solely a game phenomenon and not reflective of general troll culture.
Wriggling days are the Troll equivalents of Earth birthdays, occurring once for each Troll each solar sweep. It just so happens that at the beginning of Act 5 Act 1 we see Karkat Vantas's wriggling day, on "the 12th bilunar perigee of the 6th dark season's equinox", making him 6 Solar Sweeps (13 Earth years) old. The other Trolls are presumably all the same age as Karkat. Trolls apparently view their wriggling days as opportunities to lament their insufficiencies. This may be an idiosyncrasy unique to Karkat, though.
12th Perigee's EveEdit
12th Perigee's Eve is the Troll equivalent to Christmas, possibly with some elements of New Year's Eve. The Trolls and their Lusus may decorate the hive or just stay inside, and the Lusus goes and collects a "behemoth leaving" in the style of a Christmas tree. The "12th" perigee is probably counted in number of perigees from the beginning of a sweep, rather than from the last equinox, since
- At some point, Latula says it's been since she has done any fighting. Furthermore, Karkat , Aradia and Aranea have used the term "years" as well. From the context, it's not clear if it's used as a synonym for sweep or just a colloquial term for a vague amount of time.
- Terezi also mentions that her hive looks nice in the , indicating that Earth seasons may be used on Alternia too.