time, what is it and does it really exist?

I was having a debate with somebody on another forum and it led to the discussion of time, and whether it exists. I thought it was a good philosophical question, as it could lead to a lot of different opinions and thoughts. So, here it is!

Does time really exist, and if it does, did it exist before man? If it did, what was it? Animals and other life don't care about time, only Humans do, and only Humans ever will...

It may be something mankind named, but is it real? Humans found a way to measure it that part is clear. Did we create time or simply find a way to measure it? Scientists theorise about time travel, but is time actually real? Is time travel impossible because time doesn't really exist?

Do Humans' have a real sense of time without a clock? is the use of the sun and the moon a factor in it if we do? in our heads we can estimate the time but using our last interaction with a time-piece.

Hmmm . . .

I think without time, everything that ever has been, is, and ever would be, would exist in the same moment, thus destroying the universe - bizarre but I think it could be true. Time allows separation of separate entities. Without time, nothing could come before or after, it would all be here now.

I think time exists.