I would also suggest cheats but not necessarily for items.
Without checking then chances are the date and time is in some obscure part of hardware that needs to have all nice reading and pleasantries done to it, as well as wait. Most games in most consoles with anything like this will copy this to normal memory and operate on that instead, possibly once at the start of the session (and then every frame a number added to a counter to "keep up" as it were) but also possibly all the time (or near enough as makes no difference/faster than human reactions and timeframes).
Either way it will be in normal memory at that point so you can concoct a use this button combo to set time to this, or use this button combo to add/subtract however many days/hours/whatever. It should then be isolated to the game itself rather than system level and dodge issues with other games when you forget/can't be bothered to change back.
I don't know what the time format used will be either -- could be something abstract like old dos formats, could be something like unix time, could be some combo of the two (one second since 1970s makes for a reasonably large number and annoying to handle, one second and then change when a new day arises is a different matter entirely. Also potentially a nice option to add a lot of time on quickly without worrying about per second things).
It is a potentially more annoying cheat to make. You hope the idle in a corner, see what changed, idle in the corner, see what changed, idle in the corner, see what changed... routine can narrow it down but it will not always be the case.
If you are better at hacking to the point where you can handle a basic tracing session (this would be a wonderful learning experience for that as well) then you can consider the debug route -- if whatever item you want appears on sale or whatever as a consequence of the time then find the items on sale/available/whatever as a normal inventory, shop, chest contents... style cheat search and part of it getting to that point will necessarily involve the time being examined. Alternatively as started out with the time hardware is likely some fixed aspect in hardware (or software calls to the underlying operating system as it were) and thus anything reaching out and touching that, possibly then whatever that is copied to*, then anything reading those becomes something to look at.
*for various reasons then control data is not supposed to be used in the direct hardware locations the documentation will mention but instead copied to normal memory (a process called debouncing, named for one of the failure modes it dodges) and operate from that. I did not want to use the term debouncing here as it might not technically be accurate but if you read up on control hacks then you find a very familiar process to what this will look like for time.
I was gonna say that. lol
