With a title like that, you might be wondering if you’ve stumbled onto a master’s thesis but the topic at hand is how to describe distance, size and time in a fantasy story. Being creatures of the 21st century our inclination is often to talk hours, minutes, seconds, feet, miles, and so on. But is this really a good fit for the fantasy novel? As with most things, it depends.
This matters because many fantasy settings are pre-industrial and such people on Earth have different conceptions on distance and time, specifically they rarely use units of time and they are much less precise than we are in units of distance. A Mongol would almost certainly not have said “Iljuk was 11 inches taller than all the other Mongols.” He would have used a relative measurement like “Iljuk stood a head taller than everyone else.” How big is a head? Who knows but it conveys all the reader needs to know about Iljuk: he’s a lot taller. Is it really important to the story that we know he was taller by 11 inches exactly? Almost certainly not.
Worse, many readers (myself included) would consider this a negative when scanning a book. If everything else shined, it might be overlooked but it hints at other problems and anachronisms in the setting. The thing is, such precision is usually not appropriate (unless your fantasy civilization is very advanced, like the Atlantans) and easily replaced by relative measurements. Also, don’t fall into the trap of just creating other precise measurements. I recall in Dragon Riders of Pern a reference to “beats of a dragon’s wings”. That might be appropriate in some settings but in many would the characters really be so concerned about counting such fleeting passages of time? Wouldn’t they probably just say “a few moments?”
In a fantasy novel would you say something was as loud as a freight train? Probably not. What would someone in that fantasy world know about freight trains? So why speak of inches or minutes when they probably would have said hand-span or “a while.” (Of course, the train simile was used in one of the best-loved fantasy novels of all time. I love it myself but still cringe every time I read that sentence.)
Would an illiterate tribesman speak of hours or feet? Assuming your hunter-gatherers are anything like those on earth, the answer is not at all. There are dictionaries available of various hunter-gatherer languages and they don’t have many precise units of measurement; it wasn’t necessary to them. (They don’t have many words at all actually. Unwritten languages often had well under 10,000 words in total.)
What about literate pre-industrial civilizations like the Ancient Romans or Greeks? Here it is more mixed. Most ancient civilizations did have units like miles and smaller units like cubits and the like. These tended to go hand in hand with sophisticated construction. Certainly by the time they were building grand monuments, they had a need for many units of distance and many developed or borrowed sophisticated geometric techniques and therefore angular measurement, terms for shapes, etc. But caution is still required because these units were often the provenance of the specialist: the engineer, the construction foreman, the soldier, merchants and so on. Would the average innkeeper or farmer use precise distances? Perhaps, perhaps not. It depends on the setting. Certainly a farmer might speak of a unit based on plowing a field like a furlong but maybe cubits and miles would be less common for said farmer (or very imprecisely used: remember the old saw about the “country mile”?).
How about time? Here it gets a little trickier, although in many ways simpler. While units of distance are well attested going well back into history, units of time are more problematic. The concept of hours is very old on Earth but in most usages it was a variable hour: daylight was divided into 12 hours and night was divided into twelve hours. Except near the equator, that means an hour of day was not an hour of night (except at the equinox of course) and it changed every day.
Yes, there were sundials but as an example of how little hours were use by the common man, the Romans pilfered a sundial from Egypt and didn’t bother correcting it for Roman latitude (at least for a time). Fixed units of time might be used (as for instance a turn of the hour-glass used for Roman legal cases) but that was a special use in a special place. The average person would not speak of a certain time of day or something lasting for a certain number of hours (or turns of the hour-glass); it wasn’t a common way of thinking.
Monastic time for well into the middle ages followed the variable hours: day and night were partitioned into so many units making the night hours in a Irish monastery come distressingly quick in the summer.
In fact, for time, it wasn’t common for people to use a fixed meaning of time and a fixed hour of the day until clocks became prevalent: thus our six o’clock: six of the clock. And it was quite a while before hours were subdivided into quarter hours let alone minutes. Second (short for second minute or second sub-division of 60) took even longer. It was high Middle Ages (~1200s) before clocks started becoming common in towns (on a tower with hours sounded by a bell long before there was actually a dial showing hours and later minutes).
For a great survey of how the concept of time and distance changed over history see The Discoverers by Daniel Boorstin. It’s almost 30 years old now and some fault it for Euro-centrism but as a primer on the different perceptions of time, place, distance and many other things it is invaluable, especially to the fantasy writer. After you read it, you may be quite reluctant to toss “minutes”, “seconds”, and so on into your fantasy opus.
Will your illiterate griffin rider speaking of seconds doom your book sale? Maybe not by itself. But it will be flagged by some readers skimming it in a bookstore and some agents considering whether to represent. Why take the risk? At the very least, make a conscious decision to be precise or not, one that is appropriate to your setting rather than simply toss in the units of measurement without thinking about it. To some readers, such a reference is as discordant as having your primitive warrior talk about “going nuclear.”