Ideographic: When the sun is a foot 尺 above the horizon 旦Radical:

meaning for zhòu:

  • - daytimeday and night
  • - period of 24 hours
  • - continuously, without stopdaytimenocturnal
  • - to hide by day and come out at nightday and night without rest (idiom)(In summer) the days are long and the nights short. (idiom)