Indeed. Time is subjective as well, we all experience time subjectively.

And what we call "objective time", being 1 second = radiation of Cesium 133 atom, well how do you know that the Cesium atom radiates at the same intervals? If you measure it, how do you know that the measurement device is correct? How do you know that your interpretation of the measurement is correct? See it all boils down to subjectivity in the end...