Are space and time properties of our perception according to to Kant?
Kant's Critique of Pure Reason distinguishes the way we arrive at knowledge via a pair of binary distinctions. The first is the synthetic-analytic distinction. We know certain things analytically because they are contained in the very concept of the object being known, i.e. we know that cats are quadrupedal mammals because four-leggedness and being a mammal inhere in the definition of cats. However, we know the possible colors of cats' fur synthetically, because no particular fur color is inherent in the concept of "cat" -- we must look at cats to obtain this knowledge. Another distinction made by Kant is the a priori-a posteriori distinction. Things such as mathematical concepts are known prior to experience (a priori) and, in fact, experience has no bearing on them, while other things, such as the colors of cats are known from experience, or a posteriori. There is ordinarily a strong correlation between things we know a priori and analytically and those we know a posteriori and synthetically.
Space and time, however, are known a priori, in the sense that we know do not derive our knowledge of them from experience. However, space and time are not themselves known analytically but synthetically, and thus are what he calls synthetic a priori concepts, elements of our experience but prior to our experience. As all of our experiences are spatio-temporal (one could not imagine an object that wasn't extended in space and time as it would not be an object), Kant thus describes space and time as conditions of our experience. This isn't quite the same as space and time being properties of our perception, because we do not perceive space and time per se, but rather we structure our experiences in terms of space and time; for Kant, they are conceptual scaffolding shaping how we understand phenomena.