I would consider it rebloom.
The American Hemerocallis Society defines reblooming as "Having more than one cycle of flowering per year". That would seem to apply to each cultivar rather than to each fan or plant of a cultivar. So if one had two clumps of the same cultivar and one clump started flowering in June and ended on July 1 and the second clump started flowering in August and ended on September 1 then that cultivar rebloomed.
One of the things that can happen is that a fan starts to produce a scape and then something happens to the scape and it dies (is aborted for some reason). It may be aborted while still very small and not seen by the gardener. The fan may then rebloom and it would appear as if it was the first scape. Of course, if it did not flower from the true first scape then that fan could not have shown more than one cycle of flowering in that year. Nevertheless, the clump could show a second cycle of flowering and therefore the cultivar rebloomed.
Researchers have determined that the majority (all the cultivars they tested, but with tens of thousands of cultivars it is impossible to be certain that they all act the same) of daylilies do not need to experience cold to flower and they do not need to experience specific day or night lengths to flower. That means that a daylily fan will more or less flower when it becomes "mature" (probably when it reaches larger than a specific size for that cultivar). That means that daylily fans may flower at any time of the year (when the weather is okay for growing) and they may do so repeatedly in a single year if they grow fast enough after flowering and it is not too late as far as good growing weather is concerned. I would have to assume that the arrival of winter does not set growth and development of scapes back to zero (it does not for example kill them), but it might if they are too large when killing temperatures arrive.
