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.

Now, I would take up a couple of examples for illustrating the use of transit for rectifying the ascendant and the rising degree of the ascendant.
(Click here to see chart)

The native of this chart came to the undersigned for consultation and reported his birth time as 11.30 PM on 4th Oct' 1947.  His horoscope was prepared and some past events were explained for verification of the correctness of the chart. The native denied all the indications of the chart.  He was told that the birth time being reported might be wrong.  Therefore, he should check up the same from his parents.  After this he said his birth as per his parents was around mid-night.  As the indications were not matching, the next ascendant was to be tried which could have been earliest around 0030 hrs on the 5th Oct.1947.
The chart was then recast as under:-
In this chart, Saturn and Jupiter, whose mooltrikona signs fall in the dusthana houses were emerging as functional malefics.  Their transit results of the past were indicated for verification with reference to the natal position of the planets.  As Mars is weak due to its being in the sign of debilitation, the periods of exact transit conjunctions/aspects of Saturn with reference to Mars were chosen for testing.  Saturn formed exact aspect to natal Mars in the year 1991 thrice i.e. in March 1991, in Aug 1991, while in retrograde motion and in the beginning of Dec 91.  Jupiter, the sixth lord, also formed exact conjunction to the natal Mars in March, 1991. In this nativity, Saturn's mooltrikona sign is in the eighth house, which rules death, obstructions, injuries and Mars is the indicator of health.  Mars indicates health in two ways; one due to its placement in the ascendant and secondly its being lord of the sign Aries.  The weakness of Mars and the aspect of Saturn created multiple problems for the native.  In one of the instances he had infected multiple boils on his face and the other transit again caused illness due to impurity of the blood.

After fixing the ascendant as Cancer many other events were tallied.  In Sep 1969, when the functional malefic, Jupiter, transited closely the natal Sun, the native had a major mishap in his family as the Sun is the lord of the second house.  Saturn's transit over the natal degree of Venus twice in 1982 gave severe illness to his wife.

Transit Ketu's close conjunction to the natal Sun in April, 1987, gave severe sickness to the son which persisted for a long time as the other unfavorable conjunctions/aspects continued to be formed for the nativity.

Rahu's close conjunction to the sixth house middle point gave fever to the native in the first week of Sept 1992.  Based on the above rectified birth chart, numbers of other events were tallied.  Further predictions have been based on this birth chart and the incidents in life of the native are being kept under observation for fuller confidence level.
(Click here to see chart)

The native of this chart presented a horoscope made about two decades back for analysis.  After closely examining, it was found that the horoscope had been made for the year 1945 in place of the year 1944.  This was based on the lunar day and weekday narrated by the native. The rectified chart was then tried for identifying various events which almost tallied with reference to the operating planetary periods.  After sometime it was observed that some of the incidents remained unexplained in the life of the native.   The past events were analyzed and they responded to the middle point of the house being around twelve degrees in place of 3 degrees emerging as per the birth time indicated.  For the Libra ascendant, in addition to Rahu and Ketu, the only functional malefic is Mercury.  Mercury, being a fast planet, its unfavorable transit results are for short durations and cannot be used for rectification of the birth time inaccuracies.  Hence the stress for rectification of the birth time in such cases is placed on the Rahu and Ketu only.

Rectified birth chart is as under

Ketu's exact conjunction with the middle point of the ninth house in March, 1992, gave ill health to the father of the native, turned the preceptor angry and caused ill-health to the children, as Ketu aspected the fifth house, as well.   Rahu's exact conjunction with the middle point of the third house involved the native in unfruitful ventures and uncomfortable journeys.

Rahu's close transit over the middle point of the seventh house in the end of 1985, caused accident to the spouse of the native, recovery of which took around three months. Ketu's transit over the natal degrees of Saturn in January, 1992, caused serious illness to the eldest child of the native.  Ketu's close conjunction to the middle point of the ascendant in Dec 1985 caused tremendous fatigue and severe headache to the native.
(Click here to see chart)

The native of this chart presented a computerized chart as under:-

The native was dismissed from service on 23rd May, 1990, without assigning any reasons and without an enquiry during the main period of Jupiter and sub-period of Saturn.  Both the planets involved are functional malefics for this chart.  On this fateful day transit Saturn was forming exact aspect on transit Mars.  Transit Rahu was forming exact aspect with natal tenth lord.   Then there were certain other non-significant events, which indicated the middle point of the various houses, should be other than 28 degrees 56 minutes as indicated by the chart.  With the help of various incidents it was felt to be around 16 degrees, which was noted for further verification.  When Venus touched the hypothetical middle point of the tenth house at the end of March, 1991, the native's reinstatement was approved by the Minister.  Again in Nov. 1991, when Rahu formed exact aspect with natal middle point of the tenth house, the reinstatement order was suddenly withdrawn.  Based on these past events the 16 degrees was noted for future events' verification.  On 9th Sep 1992 matter was again referred to by the concerned Ministry to the Appellate authority, which proved favorable to the native.  This time Venus, which is a functional benefic for this chart, formed exact conjunction with natal tenth lord, Mars.  On 25th Sep, 1992, when transit Mercury came into conjunction with the natal tenth lord there was another favorable development in the case of the reinstatement of the native.  In addition to rectification of the reported birth time for identifying significant events, the native was prescribed strengthening remedial measures for favorable weak planets and propitiatory remedial measures for afflicting planets.   Propitiatory remedial measures are prescribed for both natal and transit influences.

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.