TIL Roman hours were not a fixed length of time but always just ¹⁄₁₂th of the daytime, so during the summer an hour could be 1½ modern hours while during the winter it could only be 40 minutes

Roman hours were not of a fixed length because they simply equal to the amount of light or darkness on a given day divided by twelve. Since the amount of daylight varies greatly from day to day over the course of the year—with perhaps as many as 15 hours of daylight in the summer and only 8 or 9 in the winter—a Roman hour in the summer might be equivalent to a modern hour and a half, and, similarly, in the winter, a Roman hour might be only 40 of our minutes long.