Cycles are everywhere. There’s the seasonal cycles founded upon the tilt of the planetary axis, and the daily cycles that derive from Earth’s revolution, to name only two classes of cycles. To a first approximation, all cycles… all the ones we humans care about, anyway… reflect some physical aspect of the planet we live in, whether that ‘physical aspect’ be the Earth’s axial tilt, its period of revolution, or whatever else it might be. And since astronomers are discovering extrasolar planets in a more-or-less steady stream, it’s only natural to wonder what sort of cycles might be associated with planets other than Earth.
   Consider a planet orbiting a binary star—that is, a planet which (like George Lucas’ Tatooine) has two Suns. If the two stars are, themselves, in close orbit around each other, while the planet circles them at a comparatively greater distance, that planet could have a basically stable orbit, as Earth does; it could have whatever degree of axial tilt, as Earth does; it could exhibit all the cycles we experience here on Earth… but in addition, this planet could have an extra class of cycles which is completely unknown to us Terrans, cycles which are derived from the motions of its two Suns.
   The most obvious of these ‘extra’ cycles would probably have to do with the two Suns’ aggregate output of energy. Any time the two Suns are both in a direct line with the planet, much of the energy from the farther Sun will be blocked by the nearer Sun; any time the two Suns are both plainly & distinctly visible from the planet, the total energy output of both Suns will shine on the planet, basically unobstructed. So in addition to whatever cycles that planet will exhibit as a result of ‘intrinsic’ features such as its axial tilt, that planet will also exhibit cycles that are derived from the close-orbit motion of its two Suns. It’s possible that there might be some sort of gravitational resonance effects which cause the planet’s orbit to be ‘locked’ to an integer ratio of the period of the orbiting stars; otherwise, the planet’s ‘bi-solar cycles’ might well be completely unrelated to its 'intrinsic cycles’.
   How would a bi-solar planet be affected by its ‘bi-solar cycles’? Alas, there’s no a priori one-size-fits-all answer to that question; it depends critically on specific details of the binary system in question. The ‘worst’ case, with two basically-identical stars whose common orbit often ends up putting the planet on a direct line with its two Suns, would have the combined energy output from the two stars varying over time by a factor of 2. That’s a pretty significant influence, but exactly how much of an influence it is will depend on the stars’ orbital period—i.e., how often (and how fast!) that energy output transitions from X to 2X and back again.
   It may be worth noting that energy-delivered-to-the-planet isn't the only thing that’s affected when you have two Suns rather than one. Each star has its own gravitational field, and the strength of this field varies as the inverse of the square of the distance; since the planet will have two orbital distances to worry about, one for each of its two Suns, it follows that the aggregate strength of the two Suns’ collective gravity will vary in a way that just can’t happen in a one-Sun system. How will the planet be affected by the varying aggregate gravity of its two stars?
   And let’s not forget that individual stars can vary in output! Earth’s Sun is, itself, a 4% variable star, after all. What if one or both of the ‘core stars’ in a binary system are significantly more variable than Earth’s Sun?
   Even with as simple a system as Earth’s, there’s enough recurring variability to encourage life-forms to ‘throttle back’ their activity/metabolism on a regular schedule. Many critters are only active at specific points in the Earth’s day/night cycle (see also: ‘nocturnal’, ‘diurnal’ and ‘sleep’); some critters hibernate their way through the colder, more-barren part of the year; there are even some critters whose activity is tied to cycles whose length is an integer multiple of the length of the year! The cycles of a binary star system could end up creating all sorts of biological niches for creatures, dependinf on which of those cycles the creature happens to be ‘attuned’ to.