Not a scientific basis, sorry.
Au contraire. LTT (Last Thursdayism Theory) is supported by every scientific finding in history*. Name one scientific fact that contradicts it.
After all, like you said,
Unless you can prove it was the same there is no need.
So go ahead, prove that time was the same before Last Thursday. 'Cause you know,
you said it.
* - You know, since last Thursday.