At what point in the solar cycle does the 20-meter band usually support worldwide propagation during daylight hours?
Why The MUF during daylight almost always sits at or above 14 MHz, so 20 meters supports F-layer skip to distant parts of the world during the day regardless of where we are in the roughly 11-year sunspot cycle. At solar maximum higher bands like 15, 12 and 10 meters open up too, and at solar minimum those higher bands often close, but 20 meters keeps working. That reliability is why 20 meters is considered the workhorse DX band.
Watch out Saying it only works at solar maximum confuses 20 meters with the higher HF bands, which really do need high solar flux; 20 meters needs far less ionization to refract signals back to Earth.
20 meters is the workhorse: daytime DX at any point in the solar cycle.