If time isn’t a measure of 60 seconds, what then is time?, is it just an immeasurable constant? or maybe we can say time is all the instants, but we can’t say time is all the times, if times are measurements of time.
The measurements of time are numbers such as times, dates and clock readings that we place on instants and on longer events, and these numbers are relative to reference frames and time zones and conventional agreements about how to define the second. It is because of what time is that we can succeed in assigning times in this manner. Another feature of time is that we can succeed in placing non-simultaneous events in a linear sequence one after the other according to their times of occurrence. A third feature is that we can succeed in coherently specifying with real numbers how long an event lasts. These are three key features of time, but they do not quite tell us what time itself is.
It is an arbitrary convention that our civilizations designs clocks to count up to higher numbers rather than down to lower numbers as time goes on. It is just a matter of convenience that we agree to the convention of re-setting our clock by one hour as we cross a time-zone. It is an arbitrary convention that there are twenty-four hours in a day instead of ten, that there are sixty seconds in a minute rather than twelve, that a second lasts as long as it does, and that the origin of our coordinate system for time is associated with the birth of Jesus on some calendars but the entry of Mohammed into Mecca on other calendars.
Talking about conventionality, the French physicist Henri Poincaré argued that time is not a feature of reality to be discovered, but rather is something we’ve invented for our convenience. He recommended the convention of adopting the concept of time that makes for the simplest laws of physics. Opposing this conventionalist picture of time, other philosophers of science have recommended a less idealistic view in which time is an objective feature of reality. These philosophers are recommending an objectivist picture of time.
Consider how we use a clock to measure how long an event lasts. We always use the following method: Take the time of the instant at which the event ends, and subtract the time of the instant when the event starts. To find how long an event lasts that starts at 3:00 and ends at 5:00, we subtract and get the answer of two hours. Is the use of this method merely a convention, or in some objective sense is that the only way that a clock should be used? This method of subtracting the start time from the end time is called the “ metric ” of time. Is there an objective metric, or is time “metrically amorphous” because there are alternatively acceptable metrics, such as subtracting the square roots of those times, or perhaps using the square root of their difference and calling this the “duration”?
So can our standard clock be inaccurate? Yes, say the objectivists about the standard clock. No, say the conventionalists who say that the standard clock is accurate by convention; if it acts strangely, then all clocks must act strangely in order to stay in synchrony with the standard clock that tells everyone the correct time. A closely related question is whether, when we change our standard clock, from being the Earth’s rotation to being an atomic clock, or just our standard from one kind of atomic clock to another kind of atomic clock, are we merely adopting constitutive conventions for our convenience, or in some objective sense are we making a more correct choice?