Maybe you should have an editable chart, which you can zoom in and out of and pan along the timeline?
Whew, glad it's working for someone! Did it seem intuitive for you w/o the directions I just posted?
I haven't seen this specific functionality anywhere else (including Coindesk), which is why I wanted to make this. It may exist, but I have yet to see it myself.
I like all the suggestions I'm hearing! But as I'm not a developer, I have to pay someone to do the real work here, so I'm not sure how much I'll be developing this. I'm mostly interested in it being functional and easy to use. For now, I think my goal is to simply have most people reporting the site works for them as intended!
Oh, and for anyone who hasn't been able to get it to work, here's what it should look like when it is working! Just fill in the BTC amount and date in the 3 2-digit fields, and the USD value should display as soon as all 3 fields have valid numbers.