Time dimension is the fourth dimension in our world after x , y and z dimensions of space.
Time is always positive and increments always in real time/real life. Only in a virtual world, the time can be negative. In space, the length, width and height dimensions can be positive or negative. We can always look straight ahead in front of us as well as behind us, on both sides of origin.
Time measurement is dependent on gravity and speed of the object on which the clock is mounted. Clocks on Earth's surface measure differently on a spaceship. The same clock will measure differently when taken on a space shuttle, geostationary satellite or GPS or Galileo satellite.
A clock on a revolving satellite in an orbit is supposed to be slower as viewed from the reference of the clock on a stationary object.