"On the Reckoning of Time" ("De temporum ratione") included an introduction to the traditional ancient and medieval view of the cosmos, including an explanation of how the spherical earth influenced the changing length of daylight, of how the seasonal motion of the Sun and Moon influenced the changing appearance of the new moon at evening twilight. Bede also records the effect of the moon on tides. He shows that the twice-daily timing of tides is related to the Moon and that the lunar monthly cycle of spring and neap tides is also related to the Moon's position. He goes on to note that the times of tides vary along the same coast and that the water movements cause low tide at one place when there is high tide elsewhere. Since the focus of his book was the computus, Bede gave instructions for computing the date of Easter from the date of the Paschal full moon, for calculating the motion of the Sun and Moon through the zodiac, and for many other calculations related to the calendar. He gives some information about the months of the Anglo-Saxon calendar.