The beauty of the world and the orderly arrangement of everything celestial makes us confess that there is an excellent and eternal nature, which ought to be worshiped and admired by all mankind.
Beauty's a doubtful good, a glass, a flower, Lost, faded, broken, dead within an hour; And beauty, blemish'd once, for ever's lost, In spite of physic, painting, pain, and cost.
The epithet beautiful is used by surgeons to describe operations which their patients describe as ghastly, by physicists to describe methods of measurement which leave sentimentalists cold, by lawyers to describe cases which ruin all the parties to them, and by lovers to describe the objects of their infatuation, however unattractive they may appear to the unaffected spectators.
I can only note that the past is beautiful because one never realises an emotion at the time. It expands later, and thus we don't have complete emotions about the present, only about the past.