What is time? Is it linear or cyclic?

My contention is that some regard time as an arrow or linear while some religions regard it cyclic (Kaal-Chakra). Also in his latest book, “The Grand Design” Hawking said: “Because there is a law such as gravity, the universe can and will create itself from nothing. Spontaneous creation is the reason there is something rather than nothing, why the Universe exists, why we exist.” By inference and reference to his love of M-Theory, time may be considered as cyclic. Time starts when forces (super-gravity) and matter procreate themselves into universe spontaneously and it ends when big crunch occurs and again starts with the big bang spontaneously produce space.