Final answer:
The navy expresses days using formats that include the Gregorian calendar, the 24-hour clock, and nautical time involving the International Date Line, with time tracked in terms of solar days, and standardized into 24-hour periods.
Step-by-step explanation:
The question asks how days are expressed in the three formats used by the navy. In assuming a naval context, let's consider a couple of common timekeeping methods that might be analogous to 'formats' in how days are represented: The Gregorian calendar, the 24-hour clock, and nautical time, which involves time zones and the International Date Line. For instance, when crossing the International Date Line, the calendar date changes by one day; to the west, it decreases, and to the east, it increases. This reflects the global need to maintain a rational system of timekeeping despite the fact that the natural time intervals of day, month, and year are not commensurable (they don't divide evenly into one another). Time is tracked in terms of solar days, observed through the apparent motion of the Sun, and by the standardized 24-hour clock, allowing for periods such as AM and PM.