Birth chart rectification means rectification of birth time inaccuracies.  There are a few theories prevalent but none of them helps us in giving accurate results. The birth time rectification technique as devised by the author is not a one-time exercise but has to be taken up in a phased manner. This is based on the transit of the functional malefics over the natal weak planets and the middle points of the houses where mooltrikona signs of weak planets fall.  Under the Systems' Approach, degree rising in the ascendant is treated as the middle point of each of the twelve houses.  The functional malefics are those planets, whose mooltrikona signs fall in the dusthana houses.  Besides functional malefics, Rahu and Ketu always act malefically for everyone so far as their transit over natal weak areas is concerned.

 Rectification has two dimensions i.e. rectifying the rising degree in the ascendant and sometimes rectifying the ascendant itself.

First of all, identify weak planets and functional malefics in a chart.  Then see the transit position of functional malefics with reference to the ascendant over the weak positions. Note the houses where the exact conjunction or aspect is likely to be formed with the middle point of a house having mooltrikona sign of a weak planet in the near future.  Keep a watch at what degree the extreme unfavorable results are felt and note down the same for the purpose of rectification.  To test whether the degree noted by you is the middle point of the house you have to repeat this exercise at least twice with reference to the identified degree.  If each time on subsequent occasions transit effects of functional malefics create unfavorable results at the degree identified, the degree of the ascendant/lagna will have to be modified accordingly. Roughly one degree of ascendant means a difference of 4 minutes in the time of birth. Taking into account this degree of the ascendant and the tentative time, the birth chart will have to be reworked.

This technique is very useful for:-

A) Identifying significant events likely to happen due to exact/close aspects/conjunctions of functional malefics with middle points of the weak house/planets.
B) Identifying significant events likely to happen due   to close/exact aspects/conjunctions of functional benefics with middle points of the strong houses/planets.
C) To answer queries of recovery from illness.
D) To answer questions for expected favorable results if exact conjunction/aspect of functional benefics is likely to take place in the near future.

The technique of rectification of birth time gives excellent results and establishes astrology as a science.  This is one of the tools which becomes base and helps us in identifying significant events.