  In the cosmological context an effective quantum field theory describing the
behavior of visible matter in the universe is characterized with its inherent
UV cutoff and also with an IR scale that is set by the cosmological (particle)
horizon. This UV - IR relation naturally defines a space-time grid over a
horizon scale. Using the approach for determining of dark energy through the
space-time uncertainty relation versus such a space-time grid, we estimate the
energy density and pressure of a dark energy defined by this UV - IR relation.
Such a dark energy shows up to decay linearly with time and exhibits a negative
pressure only recently.
