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; the recorded timestamps are UTC, and every hour is converted to Eastern Time (US) before counting. All dates in the sample fall in daylight time, so the shift is 4 hours.
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.