one advice, develop the website, rather than selling, develop website, add each day historic events, one day, it will be full of one online calender domain, and for example
1january, list all the historic and in bottom of page provide the link to 2january.
develop the website, make it open to public, who want to list their birthday comments on ur site, i think if you have all the dates, it can be put to a great use, and you can then resell you sites, its ganna be alot of money.
Make users, if someone has birthday, put it on ur site, off them some kind of promotion like, to be out the pick on the front of ur page, i mean there are so many things you can do.
Think about ideas, it wont be worth selling, but it will be worth making, and runniing the site, you will definately get alot of money.
you can make something like, i-got-each-day-of-calender-online-portfolio-.
It can gain popularity if you have all the each date domain. it can be big. just rethink before you sell, it can be a great assest.
Good luck.