The question of evidence... did the Egyptians use pi, Phi, or Right Ascension?? Who knows.
Do you know of any other ancient culture's methods, in terms of RA or other system?
If it could be found that a certain number of degrees or minutes was in fact a significant fraction of the number of hours of darkness at a specific time and place (date and latitude) then that could be a start. You can't get a whole night which is at a Phi ratio of the full 24 hours any further south than Greece, but you could perhaps get a star rising to a certain point in the sky or other such observable phenomenon which marks a significant proportion of the 24 hour period, no matter the method used in those times to divide up time or space in the night sky.
Perhaps the old obsession with the precise duration of night and day was a mainly thing of northern climes. On Tuesday, March 17th, in Ireland, especially at Skellig's latitude, we will have exact ratios of night and day (sunrise to sunset). I reckon that's the root of the Patrick's day stuff. Perhaps at lower latitudes, where the difference between a length of day in summer and winter isn't so great, it's no big deal and never was. Then again, perhaps in every part of the world where the sun was once worshipped, the number of minutes in a day was closely observed, and consequently, certain dates of the year were celebrated, for having a certain ratio of light and darkness.
Such a strange idea when you think about it, 1,000 loaves of bread.