Den Cathy Beck can flower any time of the year.
I posted this link before of the Univ of Hawaii's results and there is a graph on the bottom of frequency of flowering by month
Hawaiian Floral Nursery: University of Hawaii cultivars
As to your antelope Dens, the answer varies some for the type. I grow mostly Canaculatum types and these grow and flower throughout the year. These flower heavily from June to January and grow new canes at the same time. I especially like them since they flower 2-4 times a year on multiple canes and numerous long lasting flowers.
My Den Pixie Princess is early this year and one pot has six spikes already.
This photo only had 4 spikes
Many others antelopes commonly seen are crossed with Den Jacklyn Thomas which gives them a lot of good features (smaller; compact; year round flowering; tall flower stems; and long lasting cut flowers) but moves them from the pure antelope group.
Most Dens are breed for the cut flower trade.