(1) Simply inscribe your knowledge of any large scale events (disasters, discoveries, etc etc) over the next six months (there should be at least one memorable example) into a text file.

(2) Encrypt said text file.

(3) Give text file to a custodian. I sure Art Bell would volunteer, he’s very interested in time travel.

(4) In six months time give Art the encryption key and he can reveal what you said.

Easy !

It doesn’t affect any timelines for that covered six months.
Art can’t peek, even if he wants to, which he probably would.

Thanks,
Simon.