Conception Zodiac
Conception Zodiac support
Last updated 15 September 2026.
Conception Zodiac works out the zodiac sign that was overhead when a pregnancy began, rather than the familiar one from the day of birth.
How it works it out
Obstetric dating counts gestational age from the last menstrual period, and conception follows about fourteen days after that. So the conception date is the birthday, minus the gestational age, plus those fourteen days. At full term, which is 280 days of gestational age, that comes to the birthday minus 266 days.
Why it asks how early or late the birth was
Because that is the only part of the answer you cannot guess. At full term the conception sign is simply the birth sign moved along by a fixed amount, three signs for about three quarters of birthdays and four for the rest, which is barely more than a lookup table.
Gestational age is what makes it personal. Measured against the full term assumption, a birth at 37 weeks changes the sign for around two thirds of birthdays, and a birth at 34 weeks changes it for every birthday, because a shift of five weeks is 35 days and the widest sign is only 31 days long.
If you do not know it, this is the question worth asking a parent, or looking up on a birth record. It is usually written as a number of weeks.
Why more than one sign is shown
With the gestational age unknown, the honest answer is a set rather than a single word. Term alone spans 37 to 42 weeks, which is a range of 35 days, and the conception date can therefore fall in two signs, occasionally three.
So the app commits to the 40 week sign as the headline and shows the other possibilities underneath as an open question, rather than either hiding the uncertainty or refusing to answer. Give it a gestational age and the question closes: there is then exactly one sign, and nothing left to ask.
What it is not
Conception Zodiac names a sign. It does not state a conception date as a fact about anybody. Conception dating is a real obstetric instrument, used in pregnancy dating and cited in paternity disputes, and this app is not that. It is not medical, it settles no questions about parentage, and it should not be used as evidence of anything.
Your data
The answer is arithmetic on a date. There is no account and no sign-in screen, no server and no database, and nothing you enter is uploaded or shared.
Contact
One person reads that, so a reply may take a few days.
Conception Zodiac is published by Jeffrey L Carrier.