Title says it all.
is it last year's chard EJ? the leaves seem very dark on that particular one-mine are more green with the red ribs.
Last mid/late summer. I find, as I have no 'extra' water on site that sowings/plantings of these leafy veggies really need to be made early - like nowish, then again late. I planted them in the shade of my beans and they have provided us with leaves and stems all winter long. It is incredibly red, almost ornamental!