Show Time-frame on Chart Exports

Currently if you export a chart as an image, the only date reference available is the x axis which give you a general idea of the timeframe but not the exact start date and end date.

Wholesalers are starting to distribute charts more often and it's common for them to use a custom timeframe. When doing so, one viewing the chart would have no idea what the start and end dates were for the period they are looking at. Displaying this on the exported charts would be extremely beneficial.