Lunation is the mean time for one lunar phase cycle (i.e., the synodic period of the Moon). It is on average 29.530589 days, or 29 days 12 hours 44 minutes and 3 seconds. The length of this cycle is linked to many phenomena in nature, such as the variation between spring and neap tides (the extreme highest and lowest tides, respectively). In a lunar calendar each month corresponds to a lunation.