@antoyo indeed, the code in batrachomyomachia will [run git format-patch](https://forge.sourceware.org/forge/batrachomyomachia/src/commit/f5fac826475293deabceb5f4d0b7b1eba88530cb/batrachomyomachia/local_git_ops.py#L549) and then [send the generated emails](https://forge.sourceware.org/forge/batrachomyomachia/src/commit/f5fac826475293deabceb5f4d0b7b1eba88530cb/batrachomyomachia/email.py#L81) without further changes to the Date.
My perl is rusty but I think what happens with git send-email is [that patch emails lose the date generated by git format-patch](https://github.com/git/git/blob/821f583da6d30a84249f75f33501504d597bc16b/git-send-email.perl#L1571). I should add a ticket to sort this out. -- https://forge.sourceware.org/gcc/gcc-TEST/pulls/87#issuecomment-2537
