Chronal dynamics predicts: p = ħ/(cτ) is the fundamental relation from which E = pc, λ = h/p and Lebedev's experiments follow. It is shown that the postulate of energy-dependent time τ(E) = ħ/E in combination with the classical expression for the momentum of a photon p = E/c uniquely leads to the relation p = ħ/(cτ). This relation is identical to de Broglie's formula for a photon (p = h/λ), if we take λ = cτ. Thus, the de Broglie wavelength is not a fundamental property of a particle, but a projection of its chronal quantum into space. offers a new interpretation of the pressure of light as the pressure of the flow of chronal rhythms.