Publication Heatmap methodology
The heatmap is a dated sample of releases with a usable, non-midnight publication timestamp from PR Newswire, PRWeb, Newswire and Send2Press. It counts source-recorded day/hour cells; it does not normalize those fields to one time zone.
The sample is PR Newswire-dominant and is not an equal-weight industry average. Sources lacking usable clock-time fields are excluded. It is a congestion signal only and does not measure coverage, pickup, or journalist interest.