The type is "duration", not "seconds". "seconds" is the unit. You can think of the unit as an operator that converts an integer to a duration. The advantages a

The type is "duration", not "seconds". "seconds" is the unit. You can think of the unit as an operator that converts an integer to a duration. The advantages are: - An integer doesn't tell you if you are talking about seconds, milliseconds or anything like that. What does sleep(500) means? Sleep 500s or 500ms? sleep(500_ms) is explicit - It provides an abstraction. The internal representation may be a 64-bit number of nanoseconds, or a 32-bit number of milliseconds, the code will be the same. - Conversions can be done for you, no more "*24*60*60" littered around your code if you want to convert from seconds to days, do fun(1_day) instead. - Safety, prevents adding seconds to meters for instance. Ideally, it should also handle dividing a distance by a duration and give you a speed and things like that. Under the hood, it is all integers of course (or floats), which is all machine code, but handling units is one of the things a high level language can do to make life easier on the human writing the code.