i picked up this fairly inexpensive date stamp and a miniature ink pad at an office supply store a few years ago and it has proven to be one of the best homeschooling investments i have yet to make.
while we aren't required by our state to keep many records of our homeschooling progress, i like to keep track of my children's development. so i put the date on every tangible piece of school work they do.
i'm not spraining my wrist writing the date by hand or anything, but this little stamp has made date-tracking a lot easier and more fun. the process of turning the inky dial and stamping the numbers on the page makes it all feel very official. and the kids love to do it, too.
even when i require my daughter to write the date out formally on her paper, i still mark it with the date stamp for OCD uniformity purposes.