1 files changed, 45 insertions, 0 deletions
diff --git a/challenge-132/abigail/lua/ch-1.lua b/challenge-132/abigail/lua/ch-1.lua
new file mode 100644
index 0000000000..a13cd4cf89
--- /dev/null
+++ b/challenge-132/abigail/lua/ch-1.lua
@@ -0,0 +1,45 @@
+#!/opt/local/bin/lua
+
+--
+-- See ../README.md
+--
+
+--
+-- Run as: lua ch-1.lua < input-file
+--
+
+function int (x)
+    if x > 0 then
+        return math . floor (x)
+    else 
+        return math . ceil (x)
+    end
+end
+
+function g2j (Y, M, D)
+    return (int ((1461 * (Y +    4800 + int ((M - 14) / 12))) /   4) +
+            int ((367 * (M - 2 -   12 * int ((M - 14) / 12))) /  12) -
+            int ((3 * int (((Y + 4900 + int ((M - 14) / 12))  / 100))) / 4) +
+            D - 32075)
+end
+
+function j2g (J)
+    local e  = 4 * (J + 1401 +
+                    int (int ((4 * J + 274277) / 146097) * 3 / 4) - 38) + 3
+    local D =   int (((5 * (int ((e % 1461) / 4)) + 2) % 153) / 5) + 1
+    local M = ((int  ((5 * (int ((e % 1461) / 4)) + 2) / 153) + 2) % 12) + 1
+    local Y = int (e / 1461) - 4716 + int ((12 + 2 - M) / 12)
+    return Y, M, D
+end
+
+local julian_today  = g2j (2021, 9, 22)
+local output_format = "%04d/%02d/%02d, %04d/%02d/%02d\n"
+
+for line in io . lines () do
+    local _, _, Y, M, D = line : find ("([0-9]+)/([0-9]+)/([0-9]+)")
+    local julian_then = g2j (Y, M, D)
+    local Y1, M1, D1 = j2g (2 * julian_then  - julian_today)
+    local Y2, M2, D2 = j2g (2 * julian_today - julian_then)
+
+    io . write (output_format : format (Y1, M1, D1, Y2, M2, D2))
+end