The heatmap shows the activity as reported by the RBN (CW/PSK/RTTY, no FT8) of the last 12 months. You can scroll back to January 2015.
Note: This is not a proper callsign. T2DE is the prosign <DO> (which initiates Japanese Wabun code) sent with wrong spacing, plus DE. Skimmer spots appear if a station calls CQ DO DE JA... but does not use exact spacing, i.e. sends CQ T2DE JA....
Daily activity is measured by the number of active hour slots (24) times band slots (13, 160m - 2m incl. WARC and 60m) and the number of continents in which a skimmer spotted the station in the respective hour, for a maximum daily score of 24 * (13 + 6) = 456. When filtering by band, the continent information is omitted, because it's only saved once per hour slot, not per band.
Click a single day on the heatmap to see its details.
<a href="https://rbn.telegraphy.de/activity/T2DE"><img src="https://rbn.telegraphy.de/activity/image/T2DE"></a>