How store a file with a timestamp in a decentralized manner?

Hi,

I'm looking for a solution to archive files in a decentralized system. that would meet those requirement:

• FLOSS
• date-stamp the upload of the file.
• immutable storage ~ WORM
• anonymous (like TOR)

I was considering IPFS but it does not date-stamp the upload :'( you can make a description-file but this is unreliable, as you can set any date..

I'm lost between hyphanet.org and Freenet.org ?!
are those the same project ?

According to A.I:

Hyphanet is focused on secure, private, and efficient communication and data sharing, with an emphasis on enabling users to monetize their data while maintaining control over their data sovereignty.

is that true ? I can't found the information on their website...