If the birth time is not provided, it is impossible to establish the ascendant degree with accuracy. Only when the individual knows the birth time range is within a few hours can the birth time be corrected by linking prior occurrences to the horoscope and planetary periods. The problem is that most people don't know how long they were in labor or even if they had a natural or c-section delivery. In addition, most hospitals don't keep track of this information for each patient. It is also difficult to estimate the birth time range because many factors may have affected when the baby came out of the mother's body including date of birth, location, length of pregnancy, number of pregnancies, previous births, etc. However, there are methods used by some astrologers to correct for this lack of information. One method is to use statistical data on birth times to create a range of possible ascendants. The second method uses an approximation called "placing the moon at birth". This means that if the moon was full or new when the person was born, then their ascendant is estimated to be one place higher or lower than actually calculated. For example, if the moon was New at birth, then the ascendant would be calculated as 0 degrees Aries (instead of 1 degree). Yet another method is to assume that every person was born at midnight.