“I was wondering if I don’t know my birth time, what should I put in the astrology chart in the time space? Does it throw off the accuracy” Someone asked that on an astrology forum. In Mexico the same worry comes up: “Estoy un poco confundida con la hora de nacimiento en mi carta natal”, which means “I’m a bit confused about the birth time in my natal chart.” And on a French forum, someone complained that most online tools don’t account for the real switch between summer and winter time.
Two doubts keep coming back. Should you correct the time yourself when daylight saving time applied? And what is a chart worth when the time is approximate? The answers come down to a few simple steps.
What time do I enter: the one on the certificate, or a corrected one?
Enter the time as it’s written on your birth certificate or your baby health record, or as your family remembers it. That’s the time the hospital clocks showed that day, in that place, with daylight saving time if it applied.
Don’t take an hour off yourself. The calculator converts your time to Universal Time, the one used to calculate the sky. If you subtract an hour before typing it in, the correction happens twice and your chart ends up a full hour off. It’s the most common mistake on this topic, and it starts from a good intention.
An hour’s difference weighs a lot. The rising sign moves about one degree every four minutes on average, so around fifteen degrees in an hour. It often changes sign, and your planets change house along with it. The rising sign and the guide to the houses explain what those two markers say about you.
How does the calculator know whether daylight saving time applied?
It starts from the time zone of your birthplace, with its whole history, and never from the one on your phone. The rules have changed a lot from country to country and year to year. In Mexico, daylight saving time applied from 1996 to 2022, then was dropped almost everywhere, except in some areas near the northern border. In France it came back in 1976, and during World War II Paris ran on German time.
The calculator knows these rules, city by city and date by date. You give it the clock time and the right place, and it does the rest. Pick your birth city carefully: it’s the one that sets the time zone, even if you’ve lived somewhere else for years.
What about the hour that happens twice, on the night the clocks change?
In the fall, when clocks go back, the same hour happens twice. In France it’s between 2 and 3 a.m. on the last Sunday of October. In the spring, an hour is skipped and doesn’t exist at all.
If your birth falls in that window, the calculator uses standard time, as our readings do, and tells you so. An hour that never existed usually comes from a copying error: ask your family what was going on around it, the meal, the night shift, the phone call to the grandparents.
I don’t know my exact birth time: is my chart wrong?
It’s missing one specific part. Your planets in the signs move slowly: the Sun takes a month to cross a sign, and most of your aspects can be read without the time. What depends on the time is the rising sign, the Midheaven and the house of each planet. Without the time, there’s no rising sign and no houses.
The Moon needs a second look. It moves about thirteen degrees a day and changes sign every two and a half days. If it changed sign on the day you were born, nobody can say without the time which of the two signs is yours. The Moon sign explains why that matters so much.
In the calculator, tick the unknown time box: you then read your chart through its signs, without a rising sign or houses. To track down the exact time, it’s worth going back through your documents one by one.
Is a rounded time, “around 8,” good enough?
It depends on your chart, and you can check it in two minutes. Enter your time in the free birth chart calculator, then the same time half an hour earlier, then half an hour later. If your rising sign stays in the same sign, your rounded time holds up. If it changes, your chart has two possible versions, and a precise time is worth looking for.
Ask about the time of day too: morning, afternoon or night. A twelve-hour mistake turns a whole chart upside down.
What a reading does with an uncertain time
A reading is still possible with an approximate time, as long as it says what it treats as uncertain. An AstroLuma reading starts from your date, time and place of birth, with the history of clock times in that place. Then it tells you what your chart says about you.
✦ Once your time is settled, read what it says about you — the Adult birth chart · $29.99 USD
Frequently asked questions
Do online tools account for the switch between daylight saving and standard time?
The AstroLuma calculator does. It applies the history of clock times in your birthplace, date by date. You enter the clock time, without correcting anything.
Should I subtract an hour if I was born during daylight saving time?
No. Enter the time on the certificate. The calculator does the conversion, and a manual correction would do it a second time.
What should I put in the time space if I don’t know my birth time?
The time on your birth certificate. Failing that, the one in your baby health record, then your family’s memory, with the time of day. And the city you were born in, for the time zone.
I don’t know my birth time at all. Is my horoscope still accurate or useless?
Your planets in the signs stay accurate. The rising sign, the Midheaven and the houses depend on the time, and the Moon can hesitate between two signs if it changed sign that day.
