I love the "Chic Tags" mini calenders and tags...I've ordered some that I plan on using to mark the dates on my pages.
You could also use a label maker and stick the date on, stamp the date on....or have one of your photos with someone from the family holding up a card with the date, or take a photo of the date in your dayplanner/calender.....
Sometimes I spell out the year, like they do on graduation and wedding announcements. Just for a little variety. I like the other tips mentioned here, too--I get tired of doing dates the same old way. One time, i even added "AD" to my date.
The most economical way would be a date stamp, like the Smash one. You can get it 50% off with a coupon at a big box store.
American Crafts (Dear Lizzy) is coming out with its own date stamp. They showed it at CHA. It's really cute. It has phrases in addition to dates.
I like the idea of continuity that using a date stamp could give the album.
If you were looking for another way, Simple Stories has several sticker sheets and patterned papers that have months, days of the week and numbers on them. Year.o.graphy line, of course, but I think most of their lines have date-related things. The birthday line does as well. I think the alpha stickers in that line have all the months of the year.