Imbolc has traditionally been celebrated on 1 February. However, because the day was deemed to begin and end at sunset, the celebrations would start on what is now 31 January. It has also been argued that the timing of the festival was originally more fluid and based on seasonal changes. It has been associated with the onset of the lambing season (which could vary by as much as two weeks before or after 1 February), the beginning of the spring sowing, and the blooming of blackthorn.