How we calculate
UmbraLux calculates every date and time on this page itself, with the astronomy library astronomy-engine – the same calculation the UmbraLux app uses for its charts. As usual in astrology, positions are measured in the tropical zodiac: the signs start at the vernal equinox and span 30° each.
A sign begins when the Sun – seen from the Earth – crosses into it: Aries at 0° (the March equinox), Cancer at 90° (the June solstice), Libra at 180°, Capricorn at 270°. Because the calendar year is not exactly as long as the Sun's cycle and a leap day comes every four years, these moments move by hours from year to year, sometimes to another calendar day.
An automated test compares all 24 sign changes of 2026 and 2027 with NASA JPL Horizons: within one minute. It checks the equinoxes and solstices against the US Naval Observatory's tables too.
Why the dates shift every year
A sign begins at the moment the Sun, seen from the Earth, crosses into the next 30-degree section of the zodiac. A solar year lasts about 365 days and 6 hours, a calendar year 365 days. So the Sun enters a sign about six hours later each year, and every leap year moves the date back by a day. That is why a sign begins on one of two or three possible days.
Signs and constellations
Western astrology measures the zodiac from the start of spring: Aries begins at the March equinox. The constellations of the same names now lie almost a whole sign away, because the Earth's axis slowly wobbles. The ranges on this page follow the zodiac of astrology, not the constellations.
Questions about zodiac sign dates
Which zodiac sign is it now?
The Sun is in Libra now, since Wednesday, September 23, 2026, at 00:06 UTC. On Friday, October 23, 2026, at 09:38 UTC it moves into Scorpio.
When does Aries begin in 2026?
On Friday, March 20, 2026, at 14:46 UTC, at the March equinox. Aries lasts until Monday, April 20, 2026, at 01:39 UTC.
I was born on a cusp day. Which sign am I?
It depends on the year and the time. For example, between 1930 and 2030 Aries began on March 20 or 21, Pisces on February 18 or 19. Our Sun sign calculator works it out to the minute from your date, time and place of birth.
Why are the ranges of different lengths?
The Earth orbits the Sun on a slight ellipse and moves faster in January than in July. In 2026 Capricorn is the shortest (29.4 days), Cancer the longest (31.5 days).
What about Ophiuchus as a 13th sign?
Ophiuchus is a constellation the Sun passes through in late November and early December. It is not a zodiac sign: astrology divides the zodiac into twelve equal sections of 30 degrees each, independent of the constellations.
By year
More calendars
Matching calculators
Sources
- astronomy-engine (Don Cross) : the calculation library the UmbraLux app uses too
- NASA JPL Horizons : reference values of our test
- U.S. Naval Observatory, Astronomical Applications : reference values of our test