Time only needs a beginning, it doesn't need and end.
Nobody can prove the Big Bang theory without-a-doubt: we only could rise theories against it, or bring facts against it, but it will stay an unproven theory forever, very similar to math theories: you can't prove them without-a-doubt, you only can give it credit currently, and because there hasn't been found any counter example yet.
Nobody can prove the Big Bang theory without-a-doubt: we only could rise theories against it, or bring facts against it, but it will stay an unproven theory forever, very similar to math theories: you can't prove them without-a-doubt, you only can give it credit currently, and because there hasn't been found any counter example yet.