I know I can see in Word what the original date of creation was (eg. 2015) but how can I find documents of my required dates without opening EVERY file to check the original date?
You can add the "Content created" date to the displayed columns in Details view, just like any other property.
You can also retain the original "Created date" when coping files to a new volume by using programs such as RoboCopy or FastCopy.
For more details, see my replies at the following discussion:
It's also possible to reset the the "Created date" from the "Content created" date for a file, or an entire folder of files. This could be handy to make browsing faster, as the Content created date must be read from the metadata of each file, while the Created date is in the file system. Of course, this is only useful for files that have a Content created property, such as Microsoft Office files. If you're interested in doing this, let me know and I'll provide a PowerShell script or a link to an appropriate utility.