Rolling periods are calculated from the init date (inclusive) plus lead time

Weekly: 7 days, e.g. if the init date is August 15, the week will start on August 15 and end on August 21.
 
Monthly: 30 days
Quarterly: 90 days 
Calendar periods are fixed to a constant period definition

Weekly: Monday to Sunday
Monthly: Calendar months
Quarterly: DJF, MAM, JJA, SON

Only complete periods are shown.

See the different ways you can view forecasts

Salient offers multiple map and table views to display forecasts and hindcasts from Salient, NOAA, and ECMWF.

Forecast View Introduction