This is something that you can do if you would like. I had dated passages the Lord had given me over the years and loved coming back across it at later dates. I feel that every entry I do, the Lord is speaking directly to me, I mean after all, the Bible is the biggest and best love letter that exists! Simply putting a date down somewhere on the page when I was done would be my finishing touch. Often times, I just hand write the date because I don’t want to pull out my date stamp, but I also have one of those that I do use regularly.
When using a date stamp, keep in mind your ink use. If you have not prepped your page then there is a good chance it will bleed through. However, if you are stamping it on top of say acrylic paint, you should be ok. And again, if you don’t care about bleeding through your pages, go for it! I have many pages in my bible that have bleed through because I was either learning or just not paying attention. It doesn’t negate the work the Lord did on my heart while I journaled.
Dating is up to you. If you are creating a family heirloom that you would like to have passed down to your kids and/or grandkids, I would consider dating your entries all the more. How amazing that your entry might be just the encouragement needed for a specific circumstance decades before it occurred. I get goosebumps just thinking about it!
Here is the one I use when I don’t hand write the date in.