I tried this on an old Mac when I was 5 years old, don't know if it still works.
1) Get your system time and put it forward by one day
2) Create a file
3) Change your system time back
4) Check your file in the File Manager. It should say it was created/last modified "Tomorrow"
I guess the modification times are not stored in the files them selfs then (at least in classic mac) ?
I think it takes advantage of how Macs, like MyBB show relative dates (ie. Yesterday, Today, Tomorrow?).
I wonder if MyBB will show Tomorrow.
Do macs still reference dates in relative manner??? As they are built upon Unix, they must be having the inherent file system features like all file creation details are attached to the file itself.
So according to what CryptWizard said when you copy the file on another mac after a year of its creation, it would say file to be a year old instead of showing its date.
That sounds funny !!
It's making a file of the future

I tried this with XP..it works but it says tomorrow's date, not the actual word.

I've never owned a Mac and the first Mac and last Macs I've used are at school. They had the time unable to be changed by normal users.
File modification times have ALWAYS been stored. It's just that the Mac looks at the file time, then at the system clock and determines a relative date to display to the user.
I took this from an old computer magazine and the title was "If tomorrow never comes..." and it was either PC World (Australian version published by IDG Communications) or Silicon Chip.