An eBay-like platform where anyone can advertise and sell their belongings, except that the emphasis is placed on and value derived from the exact age of those items.
The idea was inspired by this contribution by Michaela D and this idea by Darko Savic.
Find an item (e.g. a photograph of your hometown) that was made on the day you were born.
Find a piece of jewelry that was made on the day you met your girlfriend to give it as a gift for your meeting anniversary.
You're filming a movie that pictures a specific historical date, find original newspapers and other items that were made on that exact day or at least month or year, to make the feel of the movie more authentic, etc.
People can sell items that don't have much (if any) sentimental value to them but will have a lot of it to someone else. Any date/time could be meaningful to a particular person for a variety of reasons.
I imagine the platform could function in two ways, first - it would simply be an online place for sell-buy advertisements, except in addition to the type of the item you are searching for you'd also filter by the time the item was made (either very precise (day, hour, minute, second), or approximate (week, month, year, decade)). The seller would define the initial price and negotiate it with the buyer. The buyers could also post advertisements of what they are looking for and how much they are willing to pay for the item they are looking for. The platform would serve as a mere intermediary.
The second option - the platform could buy various "timestamped" items from people, it could offer its own prices for specific items made at specific times. The moderators or the algorithms would determine the costs depending on the demand for specific times/dates and specific items from the buyer's side. This would work a bit like the stock market. The buyers would choose from the pool of items initially bought by the platform. The prices would fluctuate depending on the availability and demand for certain items.
The two options could, possibly, be combined. I perhaps borrowed J. Nikola's idea here, but it fits this context very well.
Determining the age of the item:
This is the main issue. Some items will have timestamps on them, e.g. the manufacturing date of the product, printed on it, the date and time printed on a back of a physical, paper picture, etc. But for some the only timestamp will be the owner's memory, e.g. a person might remember the day a picture was made because he/she made it on that day, or they have different means to trace back the time – notes, associations, asking others, etc., and buyers might not trust that. This would influence the price of the item.
If a buyer found the means to independently verify the age of the item, they could then leave a positive review for the seller, telling that they didn’t lie about the age, this would make future buyers trust that seller more.