Sun Transits Through the Houses: One Lap a Year, Unequal Stays

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Once a year the moving Sun makes a full lap of the zodiac, and on the way it passes through each of the twelve houses of your birth chart. Those houses stay fixed: they are the natal Placidus cusps worked out for your birth time and birthplace. This page measures that lap for one invented chart, shows why the Sun spends very different lengths of time in different houses, and shows how strongly the entry dates depend on the birth time. The houses used throughout are natal houses only, not solar return houses, solar houses or houses relocated to where you live now.

In short, for the example chart:

• Twelve entries a year, always in order. Over thirty years the Sun crossed each natal cusp exactly once a year, always forward, never twice.
• Unequal stays. In 2026 the Sun spent 20.3 days in the narrowest house and 40.2 days in the widest. The width of the house sets most of that; the Sun's own speed, which changes slightly through the year, sets the rest.
• Nearly the same dates every year. Each entry fell on one of two neighbouring calendar dates in every year from 2000 to 2029.
• Birth time moves everything. Four minutes of birth time moved the 2026 entry dates by 16.5 to 24.4 hours; one hour moved them by about 10 to 15 days.

Educational page. Astrologist.com has no transit tool and no house-ingress calculator, calendar or report. The free birth chart shows natal positions and natal houses only. Every date below was computed offline for an invented person.

The chart and the rules

The example is Lotte, the invented person used on Mars transits through the houses: born on 27 August 1991 at 06:55 in Utrecht, on Dutch summer time (UT+2), which is 04:55 UT. Her chart has Virgo rising and Placidus houses. The free chart's calculation gives these twelve cusps, the same ones published on the Mars page, and they were checked again against the chart's code before any date was solved:

Opposite houses have the same width, which is how Placidus works; why Placidus houses differ in size explains why the widths differ at all. Her natal Sun, at 3°26' Virgo, sits in her 12th house, 1.3° short of her Ascendant.

• Targets: each cusp is used at the chart's stored value (0.01°). The effect of using the unrounded or displayed value instead is given further down.
• Moving Sun: the very routine the chart uses for the Sun (the astronomia package's apparent solar longitude), with Universal Time converted to ephemeris time in the same way.
• What counts as entering a house: the moment the moving Sun passes a cusp's longitude going forward. The Sun was sampled every hour from well before 2000 to well after 2029 and unwrapped into one continuous track, so that passing 360° at the start of Aries is not mistaken for a jump; her 8th cusp, at 355.08°, sits just before that point, and her Ascendant needs no special case because it is simply cusp number one on the same track. Each crossing was solved by bisection to well under a second.
• Window: entries whose UT instant lies from 1 January 2000, 00:00 UT, up to but not including 1 January 2030, 00:00 UT.
• Clock: astronomy first, civil time second. Each instant was found in UT and only then converted to Amsterdam time with the time-zone rules the chart uses. Entries after October 2026 are model projections.

One lap: the Sun through her houses in 2026

This table was fixed in advance as every entry whose Amsterdam date falls in 2026. Times are cut to the minute; days in the house run from that entry to the next one and are rounded to a tenth of a day.

The 4th and 5th house entries are model projections, and the Sun stays in her 5th until it reaches her 6th cusp again on 28 January 2027 at 07:21 Amsterdam time. The twelve stays add up to 365.24 days, one solar lap. The 2nd house entry shows why the clock comes second: it happened on 17 September in UT but on 18 September in Amsterdam.

Width sets most of it, speed the rest. Her 1st and 7th houses are both 20.34° wide, yet the Sun took 21.0 days for the 1st and 20.3 days for the 7th. Her 4th and 10th are both 38.49° wide, yet the stays were 37.9 and 40.2 days. The Sun moves fastest in early January, when the Earth is nearest to it, and slowest in early July: in this lap from about 1.02° a day in her 5th and 6th houses to about 0.95° a day in her 11th. So the house the Sun crosses in the northern summer takes a little longer than its equal-width partner on the opposite side.

Exactly one entry per cusp per lap, checked rather than assumed. On the hourly track the Sun moved between 0.0397° and 0.0425° an hour and never backward. Every cusp was crossed 30 times in the window, once in each Amsterdam calendar year, with no backward crossing; taken together, the 360 entries followed the house order 1, 2, 3 and so on without a single break. The gap from one entry to the next entry at the same cusp was 365.240 to 365.244 days. The Sun has no retrograde, so there is none of the back-and-forth over a cusp that Mars or the slower planets can produce.

Thirty years at a glance

For each cusp, the earliest and latest Amsterdam clock time at which the Sun entered that house in the window, compared as a date and time of year. The last column counts how many of the 30 years fell on each date.

The 2028 and 2029 extremes are model projections. The spread of a little under a day is the calendar at work, not the Sun. From one year to the next without a 29 February in between, each entry came 5 hours 46 minutes to 5 hours 52 minutes later on the clock; across a 29 February it came 18 hours 8 minutes to 18 hours 14 minutes earlier. That four-year rhythm, plus a slow drift, is the same one described for the Sun's return to its own natal degree on Solar Return Date. None of the cusps here is crossed near a clock-change weekend, so each house is entered on summer time every year or on winter time every year.

The birth time matters more than anything else

The cusps belong to the birth time. A few minutes earlier or later and the Ascendant, the MC and every cusp between them sit elsewhere, while the Sun's own yearly path does not change at all. To show the size of the effect, the twelve cusps were recalculated with the free chart's routine at six birth times fixed in advance, symmetric around 06:55: one hour, fifteen minutes and four minutes earlier and later. The moving Sun was left exactly as before, and the same 2026 entries were solved again.

Minus means the Sun reaches the recalculated cusp earlier in 2026, plus means later. The rule of thumb behind the table is simple: the cusps move about a degree for every four minutes of birth time, and the Sun needs about a day to cover a degree. Four minutes was enough to change the Amsterdam date of the entry for all 12 houses at -4 minutes and for 9 of the 12 at +4 minutes. At an hour either way, the Ascendant moved from 4°44' Virgo to 24°18' Leo or 15°12' Virgo, and the entry dates moved by about ten days to two weeks.

Every recalculated chart was still a Placidus chart. Utrecht lies at about 52° north, far from the 66° limit above which the free chart switches to Equal houses from the Ascendant and says so, as explained in chart angles at high latitudes. Changing the birth time moved the cusps; it did not change how the houses were calculated.

With no reliable birth time, there are no reliable house-entry dates. The free chart shows no houses and no Ascendant when the birth time is unknown, and this page does not substitute another house system for them. What the birth date alone does give you is covered in birth chart without a birth time, and how close a time needs to be in how accurate does a birth time need to be.

Rounding, and a second ephemeris

Taking the unrounded cusps instead of the stored 0.01° values moved the 2026 entries by at most 6.4 minutes. Reading the displayed degree and minute back as longitudes moved them by at most 19.9 minutes, because a displayed minute stands for a small range. Neither moved any entry to another Amsterdam date in this example. Against the birth-time table above, all of this is small.

The Swiss Ephemeris served only as an independent offline reference and was not used for any date on this page. Its Placidus cusps for the same birth agree with the chart's unrounded cusps to within 0.07 arc-seconds. Its Sun differs more from the chart's routine: at the twelve 2026 entry instants, the Swiss Sun was up to 34.2 arc-seconds from the cusp, and solving the entries again with the Swiss Sun moved them by up to 14.0 minutes, or 17.2 minutes with the Swiss cusps as well. The bisection tolerance of under a second therefore says nothing about the model's accuracy; read the minutes in the tables as this model's minutes. The repository's golden chart fixtures check Sun positions and house cusps to 0.05°, which is a chart test rather than an ingress-time accuracy figure.

Reading the Sun's month in a house

Astrologers usually treat the Sun's few weeks in a natal house as a pointer to where attention and visibility tend to gather for a while: the themes of the house, as described in house meanings, coloured by the Sun's associations with identity and purpose. Because it happens every year, it is read as a light, recurring emphasis rather than a turning point. If you mark these weeks at all, treat them as an optional prompt to reflect on that area of life. The Sun's passage causes nothing, predicts nothing and says nothing about health, relationships, money or any event.

Working out your own dates

1. Get your natal cusps from the free birth chart, which needs a known birth time, and write each one as a longitude from 0° Aries. How to find your house cusps walks through this.
2. In a Tropical ephemeris, find for each cusp the day the Sun passes that longitude. It happens once a year, within a day or so of the same date each year.
3. Convert the UT time to your local clock for that date, summer time included.
4. Before trusting the result, ask how good your birth time is. An error of four minutes is already worth about a day.

The general method for any planet is on transits through the houses. For the Moon's monthly return to a single natal degree rather than a lap through the houses, see Lunar Return Date. Ask the Astrologist can talk about your natal houses or a date you have found yourself; it does not compute house-entry dates.

Related articles

• Transits Through the Houses
• Mars Transits Through the Houses (the same chart, with retrograde loops)
• Lunar Return Date
• Solar Return Date (the Sun against one natal point instead of twelve cusps)
• Why Placidus Houses Differ in Size
• House Meanings in Astrology
• Birth Chart Without a Birth Time