That seems to be the Epoch/Unix time format (https://en.wikipedia.org/wiki/Unix_time). It's the number of seconds passed since 1/1/1970. You can find many tools online to easily convert from/to this format , like http://www.unixtimestamp.com/. This "date" thing in the .json seems to be used to specify when the scenario was created (so they can be sorted by "newest").
Thanks. - It would have taken me a while to figure out what that date format was. Ignore the doubled up scenarios. I've got a zipped eca and an unzipped one that I'm using for reference.
Chris how many projects do you have sitting on your hard drive? you seem to have something new everyday.