How to Find a Birthdate from Astrology Positions
Using the Ephemeris to find a date from astrology info
On this Page:
- Can you determine a date of birth given their signs?
- An example of a reverse search using an ephemeris.
From time to time, I’ve been asked whether it’s possible, given astrology data (such as the Sun, Moon, and/or planets’ positions by degree and/or sign), to figure out the date of birth. The answer depends on what and how much information you have.
While this doesn’t come up too frequently, it’s a great exercise for students of astrology since it involves understanding some of the planetary cycles and involves searching an ephemeris, a process that may not be as frequent but that is in no way obsolete!
I’ve created a short tutorial with an example. In this case, we have a list or table of a person or event’s astrology positions, which gives us more than enough information to determine the birthdate behind it:
For this example, I used the following set of astrological positions/placements:
In this case, we have all that we need, and more!
Note that there are several ways to approach this. I have shown one way that is quite efficient, as follows, but we can just as easily select a different starting point.
First step: Sun sign and degree
The first step is to zero in on a particular planetary placement. Because our calendar is a solar calendar, the Sun is in approximately the same place, give or take, each year. If you know the Sun sign and degree, then you can approximate the birth month and day, but not the year.
In this example, the Sun is at 10 Pisces 50. If you’re not familiar with the approximate date ranges or times of year of the Sun signs, lists of Sun sign dates are everywhere, including on my zodiac sign page here.
I’ve opted to use a 50-year online ephemeris from Astro.com because it’s excellent and easily accessible, but any ephemeris that shows a wide date range can be used.
Of course, any additional information about the date we’re seeking can be helpful. In this case, I am using the 1950-2000 ephemeris since I know the date is within this range.
Knowing that the Sun is in Pisces from approximately the last week of February to approximately three weeks into March, I can consult an ephemeris to judge when 10 Pisces 50 generally occurs in any year. [Alternatively, I can experiment with an online birth chart calculator]
It helps to know that there are 30 degrees in every sign. In this case, we are looking for 10 degrees and 50 minutes of Pisces, which is between 10 and 11 degrees of Pisces, and approximately one-third of the way through the sign.
While it varies slightly from year to year, we can see from the March 1950 ephemeris above that the Sun is at 9 Pisces 50 on March 1st, 1950, and 10 Pisces 50 on March 2nd. We can assume that the person with the astro positions above was born on or around March 2nd.
Note that the Sun travels approximately 1 degree a day, which jives with the knowledge that the Sun spends about a month or 30 days in a sign and that a sign is 30-degrees long.
Second step: Use Pluto’s position to determine the year of birth
This is a quick cheat, of sorts! Pluto is so slow-moving that it doesn’t travel through all signs of the zodiac in the life of a human–not even close. The Sun, on the other hand, completes its transit of all twelve zodiac signs in approximately 1 year. Since Pluto travels only a few degrees of a sign each year, we can use its degree and sign position to determine the year of birth.
It helps to know the general dates of Pluto’s transit of the signs or to consult a table/list of historical Pluto sign ingresses. Consulting a table, or even scrolling through the 50-year ephemeris as I did in the video demonstration above, you’ll find that Pluto was in Scorpio from approximately 1983 to 1995. We’re looking for 7 Scorpio 14 with the added information that it was retrograde. Scrolling through the ephemeris to a March 1/2 date when Pluto was at 7 Scorpio 14 and retrograde, we come up with the following:
Cross-checking the other positions (example, Moon in Scorpio, Mercury in Pisces, Venus in Pisces, Mars in Sagittarius), we know we have our date. We should take into account the time zone since this ephemeris is in Universal Time. We can go further and approximate the time, but for now, we can leave it at this.
There are other ways to figure this out, but I have shown what I think is the most efficient method. In this example, we had a table-full of information. If we only have partial information, we would have to take a different approach.