Add: "First Seen" and "Last Seen" columns (feature)

[guidoiaquinti]

I think that it could be very useful add 2 columns: "First Seen" and "Last Seen" in the dashboard (in date/time format, not UNIX timestamp) that explain the first and the last seen of a broken check.

[amdprophet]

I don't believe it's possible to get a "First Seen" for standalone checks because they don't have an interval cc @portertech. "Last Seen" is the same thing as "issued" is it not? Displaying the UNIX timestamps as date/time is on the roadmap.