The billing cycle feature is now available under the Edit Tariff screen, just above the TOU settings.
A cycle can have 2 to 4 periods, typically seasons.
Click on the Load link below the config to load a seasonal sample.
After saving the billing cycle the Billing view link appears between the Yearly and Summary view.
The graph and table data appears as per other aggregate views except the days are now grouped by the configured billing cycle.
Currently only the last 8 periods / 2 cycles are shown, the data cannot be sorted.