On the other hand, in Prince Valiant the GM declaring that something will happen in X days (say, a curse will come to fruition after a week, if it is not lifted in some fashion) is just colour. There are no resolution processes or framing processes that take ingame time as an input or generate ingame time as an output. The GM can narrate stormy weather that makes travel near-impossible, or a horse coming down lame, or the roads being clear of bandits such that travel is quick and peaceful, just as they have a mind to.
In my experience, a typical traditional D&D game is much closer to Prince Valiant in this respect than to Classic Traveller. An exception might be if the players are resolving a situation primarily via spellcasting, and so are on the clock of rest - rememorise spells - cast spells - repeat. This is part of the significance of spell casting as a mechanic in traditional D&D - it shifts control over the fiction out of the hands of the GM and into the hands of the players. Gygax didn't describe it in those terms, but was clearly aware of the phenomenon. So was Lewis Pulsipher when he wrote that most experienced D&D players prefer to play MUs.