There are many things in operating system functionality that are based on time progressing. There are also many applications that work based on that. I don't think that the computer ever cares about "the real time" - when you run something in Internet, "real time" might be something useful for some functionality.
If you literally mean "the same date", meaning a day in calendar, that is an operating system matter. You have not specified what it is. I'm sure you can run some script to set it up, to 1.1.2000 or whatever but that is operating system specific. Still, when time progresses, the date will change, at least when 24 hours has gone past, unless you run the script again, which may affect things in your applications, which are unknown at this point.
Also, "as I boot it", is not an exact time in a sequence of getting into a user getting logged in after powering on the system. Yet, again it is operating system specific when you can run something. Not sure if this has any relevance to you, but in Puppy Linux you can remaster the binary files that are used in the initial start of the OS (much before basic loads of the system programs or functionality, like initializing file systems). If it is OK to run the script, when user has logged in, that is easily possible in every OS.
As a summary, in the most simple case, use some scheduling that OS in question has and run a script that sets the date or time or both. More complicated matters are speculated in the above. I hope this explains somewhat.
