◑ What if my birth time is wrong?

Most birth times are a few minutes off and plenty are an hour or two off. Umbriel's free Birth-Time Wobble shows exactly what that costs: slide how sure you are, and every planet and angle grows a ghost that smears along the zodiac, inked solid where it holds and dotted where it does not.

• What you'll needYour birth date and place, and a time if you have one. A rough stretch of the day, such as morning, works too
• What you getA slider from exact to 2 hours either way, a wheel with a ghost for every planet and angle, the exact second each placement changes sign or house, a range form for people who only know roughly, and a stamp of SOLID, SOFT or COIN-FLIP on each line of the daily sky page
• CostFree, no account required

It never guesses your time. It does not rank minutes, score them or say which is likelier. It shows what is true whatever the clock said, and exactly what is undecided.

Slide how sure you are. From exact to 2 hours either way, starting from the source you gave for your time. The chart is cast once a minute across the window, and a placement whose sign is the same at every one of those minutes is inked solid. The rest are dotted, with a faint arc for where they could be.

Every change is found to the second. Where a sign or a house changes inside your window, the page halves the minute until it has the exact second and says how far it is from the time you gave. A line such as "Cancer rising until 07:38:12" is measured, not estimated.

The stamps on the daily page are measured too. Each line of the day's sky is checked at moments up to 120 minutes either way. SOLID means it never changes across them, SOFT means it changes only toward the edges (at least 3 in 4 of the moments agree), COIN-FLIP means it is nearer a toss-up. The 3 in 4 line is a choice, said on the page; the counting is not.

Only roughly? Say morning, before noon, or give two times. You get what holds across the whole stretch, what is undecided with exact times, and the one fact that would settle it, such as before or after 07:38.

The limits are on the page. It claims signs, not degrees. Mercury, Venus, Mars and Pluto use lighter formulas that have not been checked against JPL. A whole day makes the Ascendant cover every sign, and it says so rather than printing twelve spans.

Nothing is looked up. The app casts your chart, with its own engine, once a minute from 120 minutes before the time you gave to 120 minutes after, and reads the same casts over whatever window you slide to. A placement is inked solid when its sign is the same at every one of the minutes inside the window, and dotted when it is not; houses are checked the same way, separately. Where anything changes, the app halves the minute until it has the exact second. The stamps on the daily sky page work the same way: each line is checked at moments up to 120 minutes either way, SOLID when it never changes, SOFT when at least 3 in 4 of those moments agree, COIN-FLIP when fewer do. The 3 in 4 line is a choice, and the counting under it is not. Positions are checked against JPL for the Sun, Moon, Jupiter, Saturn, Uranus and Neptune; Mercury, Venus, Mars and Pluto use lighter formulas that have not been measured that way.