When a “moment” could be counted
In one traditional medieval system, an hour was divided into 40 moments. If you apply that scheme to a modern hour of 60 equal minutes, each moment comes to a minute and a half. The arithmetic is simple; the historical complication is that an hour did not always have a fixed modern length.
Why the length could change
In systems using seasonal hours, daylight and darkness were each divided into 12 parts. A daylight hour therefore lasted longer in summer and shorter in winter, while a nighttime hour changed in the opposite direction. A moment measured as a fraction of such an hour would vary with the season and with whether it was day or night.
That makes 90 seconds a useful modern conversion, not a universal medieval stopwatch reading. The number of moments in the hour was fixed in this scheme; the duration of the hour being divided could vary.
From measurement to everyday speech
The old division belongs to a world in which time could be described through different systems rather than one uniform count of 60 equal minutes. Today, “a moment” usually means a brief but unspecified interval. Its history offers a neat contrast: a word that once could name a counted fraction of an hour now leaves the length of the wait to context.
