FAQ · Cards of Destiny
The five questions every new arrival asks.
Innerglyph runs Mary Greer's Cards of Destiny math directly from the published rules. These five answers explain how each piece works so a birthday lands on a single Birth Card, a Planetary Ruling is read from a per-calendar-day table, and a 52-card cycle ticks forward from there.
Question 1
How is a Birth Card calculated?
It's a digit-sum reduction of your date of birth. Innerglyph takes the year, multiplies the month by the day, digit-sums the total, and keeps reducing until the result lands between 1 and 52. That final number is your Birth Card — your seat on the board for life.
The reduction is the same shape Greer published in birthCardFromDate(month, day, year): add year + month × day, then collapse until the answer is in 1..52. The catalog itself never moves — every Birth Card is one of the 52 entries, each tied to a planet and a short reading.
Question 2
What is a Planetary Ruling Card?
The Planetary Ruling Card is read from a per-calendar-day lookup table — one row per MM-DD — described in Greer's published reference. Innerglyph resolves your (month, day) from that table and surfaces the assigned ruling; on a cusp day (late-January, mid-to-late February, April 21, July 23, August 22–23, September 22–23) it surfaces BOTH rulings so you can read either as yours.
The shape of the formula when there is no row disagreement is planetary = ((birthCard − 8 + 52) mod 52) + 1 (seven steps back). The birthFromDate(month, day, year) helper resolves the ruling from the static table — the source of truth — and labels the row with one of three relations: single, cusp-or, or paired. The 02/17/1981 anchor sits in that table under single with PRC = 31 (Five of Clubs), preserved verbatim.
Question 3
What is the 52-day cycle?
The 52-day cycle is a PRC-anchored rotation. On your birthday anniversary the cycle starts on the PRIMARY Planetary Ruling Card and ticks forward one card per day; it wraps cleanly at 52. Day zero is the Planetary Ruling, day seven is the Birth Card, and the full rotation returns to the PRC on day 51.
On a cusp-or or paired row the PRIMARY ruling still anchors the cycle; the secondary ruling(s) live alongside on the results page. The implementation lives in fiftyTwoDayCard(primaryPrc, queryYear, queryMonth, queryDay, birthMonth, birthDay): it measures the offset from the most recent occurrence of your (birthMonth, birthDay) ≤ the query date, and adds that offset to the primary PRC, mod 52. All date math runs in UTC so daylight saving never nudges the answer by a day.
Question 4
How does the Yearly Card work?
The Yearly Card is anchored to the calendar year, not to the birthday. Each new year on January 1 the card advances one step forward; 52 years later the cycle resets and starts again. So in your birth year the Yearly Card equals the Birth Card; one year later it's the next card in the deck; in your 52nd year it's the Birth Card again.
The formula in yearlyFromBirthCard(birthCard, queryYear, birthYear) is the same shape as the other two pieces — ((birthCard - 1 + (queryYear - birthYear)) % 52) + 1 — with the offset taken from the calendar year rather than the day count. That distinction is the part most new readers miss: the Yearly Card turns on January 1, not on the next birthday.
Question 5
How does the spread comparison work?
The /spread view compares two Birth Cards — yours and a friend's — and writes two short snippets: a harmony line (where you click) and a friction line (where you grind). Innerglyph first looks up the exact pair in a curated table of common meetings; if that pair isn't there it falls back to a planet-aware template so every comparison reads like a real one and never returns empty.
The lookup lives in getComparison(visitorId, friendId): it checks SPREAD_COMPARISONS[visitorId][friendId] first, then resolves the (visitor planet, friend planet) pair — symmetry isn't assumed, so "Sun meets Saturn" reads differently from "Saturn meets Sun". Anything still unmapped turns to a neutral default template so the page never renders a blank card.
Try it on your birthday
Draw your four cards.
Drop a birthday into Innerglyph's calculator and the same five pieces above resolve into a reading: Birth Card, Planetary Ruling, today's 52-day position, and the Yearly Card for whatever year you're standing in.