The direction of the world depends on each person in the world beyond boundaries. The Earth People's Era is coming. So the calculation of years extended over BC and AD is hard. Recently I argued much about the notations related to 'Past' and 'Future' with EL participants by e-mail, and renewed the plan. Earth Language was made including respect and appreciation for ancient wisdom.
Human existence depends on memories from the past.
People in the present time tend to forget our origins and what our elders give us. When we see the symbol for above as meaning Past, we might remember to once again respect it, to look up to it. Also, we might learn to give more compassion to future generations by seeing notation 18 as meaning both Future and Down. These reasons were for making the rule plainly, and easy memorizing. Although I originally felt a little uncomfortable with using the symbol 'below' for a future image, I just couldn't use 'below' for parents and ancestors.