I heard that there is a vedic numerology and they look to your birth time and recommend your name for this numbers;

Vedic Numerology is the study of the planetary rulership through nine primary numbers. It is neither based only on your "Birth-date" nor on your 'Sun-sign'. Instead, it is based on the complete planetary configurations present in your "birth-chart" (calculated on the basis of your birth-date, time of birth and place of your birth), and therefore, highly customized.  For more specific details .. Click here

For example mine is june 23, 1986 .  23=2+3=5 (Day Number) and 2+3+6+1+9+8+6=8 (Life Number) So for 5 and 8 numerologic calculations, i am recommended for a name number 5 or 6 like name ''Jas'' (j=1 , a=1 , s=3 , 1+1+3=5) or ''Leah'' (l=3 , e=5 , a=1 , h=5 , 3+5+1+5=14 =1+4=5)... Did it sound familiar to you ?

No, the above concept is not from Vedic Numerology. What you have written .. is Western Numerology. Vedic numerology does not total up dates to find your "Day Number" or "Life Number". That is altogether different concept. In Vedic Numerology, we check the placement of various planets in your birth-chart. What houses they rule, which planets are aspecting which planets, which planets are posited with which planets .. etc. In fact, this report is prepared after taking into consideration several principles for determining the functional benefics and malefics, as told by Indian sage "Parashara", and the principles told in various streams of Vedic Jyotish to measure the exact benefic or malefic nature of the planets in your natal chart.   For more specific details .. Click here

Whats difference with numerology calculations and your calculations and which one is much more accurate and why ?

Thousands of people must have been born on 23rd June 1986. Every body will have Life-number "8" as per Western Numerology.

However, there will be 12 ascendants on this day and birth-chart would change every two hours (approx.). Planetary configurations would change. Vedic numerology based reports consider "Whole birth-chart" instead of just "Birth-date". You can imagine - which should be more accurate among them?

This number thing looks more easy but not sure if it is really accurate because there are different kinds of numerology alphabet numbers and it is hard to trust to this confusion... Will be glad if you answer my this question . (thank you)

Vedic numerology uses Chaldean (Kabbalistic) primary root number system. The Chaldean System of numerology has its roots in Ancient Babylon. This system is related to the Vedic System of India and the Kabbalah System of the Hebrew mystics. The underlying premise of Chaldean numerology is that every letter has a unique vibration. Letters are assigned numeric values, from 1 to 8, based on the vibrational value. The number 9 (nine) is considered 'sacred' and is not assigned to any letter. I have found this system working very perfectly in my practice during last 15 years. I have recorded several real-life case studies - which may be gone through at following page:
http://howisyourdaytoday.com/ incident/namesugg/index.htm

What are Jyotish (Vedic astrology) factors considered by you - while suggesting the most auspicious lucky number to a person?

This question has been dealt in much detail at a specific page. Click here to read it.

One Indian astrologer told me that among the aksharas of the Graha in choice, see which Aksharas are best placed from the Moon in the Hoda Chakra (Syllables placed in the Nakshatras). Prefer Kendra and Kona Rashis from the Moon to ENSURE good health and happiness for the child.

Yes, he is right to "some extent". While suggesting suitable sound syllables, Nakshatra auspiciousness for a person should be kept in mind. Under Vedic system, every alphabet/ syllable is said to confirm to a definite pattern of sound ("Dhwani"). Vedic astrology suggests that certain patterns of sound are more in harmony with the instance of your birth.

Each Nakshatra has 4 padas and and each Nakshatra pada has a designated sound syllable. Thus, in all, there are 27 x 4 = 108 sound syllables. These 108 syllables are grouped by me in four categories, in declining order, as follows: -

1. Syllables having the utmost harmony with person's birth star
2. Syllables having a very friendly harmony with person's birth star
3. Syllables having average harmony with person's birth star
4. Syllables - which are passive/ unharmonious to person's birth star

Alphabets/ syllables with friendly vibrations may be used for purposes such as choosing your own name, naming your business, a product, naming your house and even pets.  (Click here for a sample report)

 In one Jyotish article I read that the number of syllables in the name should be based on the Lagna being Movable (2 syllables), Dual (3 syllables) or Fixed (4 syllables). I.e. San-ja-ya is three syllables and strengthens the dual signs, whereas Vi-sti is two syllables and strengthens the movable signs.

No, I do not prefer this system. Each Lagna has its own individual character. Each lagna also has its own good and bad points. Therefore, it is the person's own individual choice that what type of characters he/she wants to acquire and strengthen more. I can not suggest a person to acquire certain characters. It is totally individual choice.

Some Jyotishis  suggest advising a name which is the same as that of the Ishta Devata, viz. if the starting syllable found is 'sa' and has to be three syllables, as the Istha Devata is Vishnu, then whilst going through the Vishnu Sahasranama you will find the name 'sanjaya'.

Yes, that's a good point BUT applicable for Hindu names only. A Muslim or a Christian or a Jew or a Japanese would not (perhaps) like to choose a name of Hindu Isht Devata (Hindu God).