dulls

“We met any number of times while I was in the village. I suppose it’s been nine years then, Itachi.”
He hadn’t been particularly close with the man. Back when Orochimaru
was still in the village, Itachi knew him well enough to say hello. They were
not friendly enough for the intimate way Orochimaru spoke to him.
“You left the village six years ago.”
“Oh my, is that so? I’ve been reborn once since then. Using forbidden
jutsu, of course.”
Orochimaru had been doing experiments on people from the time he was
in the village, so Itachi wasn’t especially surprised that he had managed to be
reborn.
“This jutsu, in exchange for offering the user eternal time, slightly dulls
your perception of time. You’ve had the experience of not being sure if you
ate a certain meal yesterday or the day before that, haven’t you? For me, ten
years is no different from ten days ago.”

Itachi Shinden Book of Dark Night Chapter 6