From d0d2ebcac5e39342986e17576c3fb8569d0c7743 Mon Sep 17 00:00:00 2001
From: Quantum <quantum2048@gmail.com>
Date: Tue, 17 Jun 2025 22:04:14 -0400
Subject: [PATCH] common: implement jdnTzolkin

---
 common/src/mayan.ts | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/common/src/mayan.ts b/common/src/mayan.ts
index 0e0d16e..1058d5c 100644
--- a/common/src/mayan.ts
+++ b/common/src/mayan.ts
@@ -58,3 +58,10 @@ export function tzolkinName(name: TzolkinName): string {
 export function formatTzolkin(tzolkin: Tzolkin): string {
   return `${tzolkin.number} ${tzolkinName(tzolkin.name)}`;
 }
+
+export function jdnTzolkin(jdn: number): Tzolkin {
+  return {
+    number: ((jdn % 13 + 18) % 13 + 1) as TzolkinNumber,
+    name: (jdn % 20 + 36) % 20,
+  };
+}