Is a light-year a unit of length or of time? It’s a unit of length but it depends on a unit of time, the year. What about a meter? “The meter is the length of the path traveled by light in vacuum during a time interval of 1/299 792 458 of a second.” So the meter depends on a unit of time, too.
We know that units of length can be measured in three dimensions. Since length and duration are directly linked by the speed of light, units of duration can be measured in the same three directions. As space is made of three dimensions of length, so time is made of three dimensions of time.
Here is an all-sky map from NASA’s Fermi Large Area Telescope (LAT) show how the sky appears at energies greater than one billion electron volts (1 GeV). The term “all-sky” means all directions of the sky. It means three dimensions of sky for light to travel in time.
Messier 82 (M82) is a starburst galaxy about 12 million light-years away in the constellation Ursa Major, which is a constellation in the northern celestial hemisphere. That is, M82 is found toward the north 12 million years of light-time away.
NOAA has several Tsunami Travel Time Maps that show the estimated arrival times of tsunamis in two dimensions. Here is an animation of earthquake travel time curves in different directions from one monitoring station. The National Weather Service has a series of maps on the movement of hurricane Katrina with evolving estimates over time in the eastern U.S.
All these maps show the multiple dimensions of time. Can you see it, too?