Actual lunar "star" (sidereal) treatment around the Earth, visible from the Sun is 27 days 7 hours 43 minutes and 11 seconds. As the Earth revolves around the Sun and, while the Moon travels around the Earth, the Moon longer goes from one full moon to the next. This full cycle of the moon visible from Earth (synodical lunar treatment), took 29.53 days.
28-day lunar month is very little actual lunar rounds treatment. For reasons more mystical than scientific, the ancients used for the 28 days of the Moon. Each day of the moon was considered the lunar parking.
Cusp of lunar mansions signify the end of one phase and the beginning of another activity. The critical moment occurs when a planet passes from one to the next lunar parking.
Dividing 360° by 28 lunar mansions means that each lunar park contains 12.85° ecliptic longitude, in degree notation is 12°51’26". The width of the lunar lot - is the approximate average daily motion of the Moon.
We begin to measure lunar mansions from the vernal equinox, or 0 ° Aries, which is the first critical degrees. Since each parking 12°51’26" then the next will begin at 12°51’26" Aries. Astrologers often rounded this value to 13° Aries, but preview the following table shows that the 12° Aries as critical as the 13° Aries. This table will explain the situation remains critical degrees and repeatability of the Zodiac in cardinal, fixed and mutable signs.