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UTC clock
In amateur radio, everything runs on UTC — logs, skeds, contests. Here you’ve got a UTC clock, local time, sunrise and sunset for your QTH, and the grey line (grayline) — the boundary between day and night around the world, along which propagation is often at its best.
The shaded area is night. ☀ = the sun at the zenith, ◎ SQ5CBA = your QTH. Along the terminator (the day/night boundary) propagation on the low bands is often exceptionally good — that’s “grayline DX”, especially on 160 / 80 / 40 m.
Why UTC: operators worldwide log contacts in UTC so logs match regardless of time zone. The grayline is a narrow belt of dawn and dusk circling the Earth — for a brief moment the ionosphere on both sides favours long-distance QSOs.
Catch an opening
Combine the grayline with current propagation conditions and catch the best DX window.