Moon ingresses, void of course periods and phases, plus planetary retrogrades, ingress spans and aspects for every body, computed in three frames at once. It began as a moon calendar and the Moon is still the densest layer; the body chips below turn it into any one body's calendar, and the month, year and decade views change the unit a span is measured against. Nothing here is a claim that any of it works. The rule being applied is stated on the page, which is the part most calendars leave out.
Tropical signs are equal thirty degree arcs measured from the equinox. Sidereal signs are equal thirty degree arcs measured from the Fagan-Bradley ayanamsa, currently about degrees away from the tropical ones. Neither of them is the sky. The real constellations are unequal, their boundaries were fixed by the IAU in 1930, and the ecliptic crosses Ophiuchus, which no zodiac contains. The Moon also has up to about five degrees of ecliptic latitude, so it strays into constellations no zodiac lists at all. Those are marked in red when they occur.
Void of course under the ingress rule turns on where the sign boundary is, so the three frames give genuinely different windows. That is the whole reason this calendar exists.
A planetary transit is a span of time, not a dot on a day, and every span on this calendar is bounded by two exact geometric events: a boundary crossing, a station, or an exact perfection. No orb anywhere. Where a retrograde carries a planet back across the same aspect it perfects three times, and the span runs first exact pass to last; where an aspect perfects once, it stays an instant, because geometry supplies no second edge and inventing one would be a third rule. That split selects itself by speed: the Sun's aspects are all instants, Pluto's are all spans, and nothing in the code knows which body it is looking at.
One honest caveat, stated here because no rendering fully removes it: a multi pass span is a claim that the same aspect recurs, not that the planet stays close. A 150 day Mars approach is bounded by real perfections and says nothing about the weeks between them, which is why the exact passes are drawn inside every band rather than smoothed over.
The mirror of that caveat covers the single pass case. Calling a single pass aspect an "instant" describes the geometry, not the experience: the perfection is a moment, but a slow body sits near that degree for days or weeks either side, and a reader is entitled to ask when the aspect is active. This calendar does not answer, deliberately, because every answer requires an orb, and an orb is a chosen convention: change the number and the window moves. The companion brief on orbs found that under traditional orbs some body is always in orb of something, one hundred percent of the time, so an honest activity band cannot be a simple on or off. The planned instrument is a graded depth curve that ships switched off and labelled as a convention, which is a different kind of object from the bands here, whose edges are measurements. Until it exists, the exact moment is the only claim this page makes about a single pass aspect.
The month grid cannot carry any of this: computed over a decade, essentially every planetary span is longer than a month, which is why the year and decade views exist and why the zoom is a set of discrete views rather than a slider. The division of labour is strict: the month view carries instants, the year and decade views carry spans, so a single pass aspect never appears at span zoom as a dot pretending to be a season, and a 200 day occupancy never pretends to fit in a day cell. Every body carries the full band engine, and the zoom level selects the layer set: a body is offered at a zoom only if its data holds at least one span as long as one cell, which at decade zoom leaves Jupiter outward. The page says which bodies it is not drawing and why, because five hundred dots would be an argument that something is happening constantly, not a rendering.
Two of these layers deserve naming. The Sun's tropical ingress bands are simultaneously the seasons and the frame of the Chinese solar calendar: the Aries, Cancer, Libra and Capricorn crossings are the equinoxes and solstices, all twelve cusps are the zhongqi, and the remaining twelve jieqi, Liqiu among them, sit at the middles of these bands. And the ten slow pairs, Jupiter outward, are counted as events rather than perfections: an approach that perfects repeatedly while both bodies retrograde annually is one episode, and counting its passes separately would overstate the layer by 2.3 times, and for Neptune sextile Pluto by sixteen. Counted correctly the slow layer runs about three events a year, and it sits in the free public data, because Saturn square Neptune is a fact about the era rather than about anyone.
One feed per phenomenon, so you compose your own view rather than accepting someone else's. iCalendar, RFC 5545, all times stored in UTC and localised by your client. Subscribing to a URL rather than importing a file means the feed updates itself.