From 444c0baa87b6edfb21c002bf9e079e10509ee0e9 Mon Sep 17 00:00:00 2001
From: Sébastien Dailly <sebastien@chimrod.com>
Date: Sun, 1 Jan 2017 15:49:42 +0100
Subject: Switched dates 0 to 1899/12/30

---
 tests/tools_test.ml | 6 +++---
 tools.ml            | 8 +++++---
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/tests/tools_test.ml b/tests/tools_test.ml
index 9afc611..b64afbc 100755
--- a/tests/tools_test.ml
+++ b/tests/tools_test.ml
@@ -68,7 +68,7 @@ module TestDate = struct
   let test_get_julian_day ctx = begin
 
     let result = Tools.Date.get_julian_day 2016 01 01
-    and expected = (Num.num_of_int 2457389) in
+    and expected = (Num.num_of_int 42370) in
 
     (* Check that the num is round *)
     assert_equal true (Num.is_integer_num result);
@@ -88,7 +88,7 @@ module TestDate = struct
         y2 m2 d2
     in
 
-    let result = Tools.Date.date_from_julian_day @@ Num.num_of_int 2415753
+    let result = Tools.Date.date_from_julian_day @@ Num.num_of_int 734
     and expected = (1902, 01, 03) in
 
     assert_equal
@@ -100,7 +100,7 @@ module TestDate = struct
 
   let test_parse_time ctx = begin
     let result = Tools.Date.from_string "1902-01-03T12:34:56"
-    and expected = (Num.num_of_string "13045069031/5400") in
+    and expected = (Num.num_of_string "3966431/5400") in
         (* =2415753.52425925925925925925 *)
     assert_equal
       ~cmp:Num.(=/)
diff --git a/tools.ml b/tools.ml
index 0cf8fe6..f4befa5 100755
--- a/tools.ml
+++ b/tools.ml
@@ -268,19 +268,21 @@ module Date = struct
     + day
     + b
     + 1720995
-(*    + 2415019         (* Shift to 30/12/1899 *) *)
+    - 2415019         (* Shift to 30/12/1899 *)
     |> Num.num_of_int
 
   end
 
   let date_from_julian_day day = begin
 
+    let shift_day = Num.floor_num day
+      |> Num.add_num (Num.num_of_int 2415019) in
 
-    let z = Num.int_of_num (Num.floor_num day) in
+    let z = Num.int_of_num shift_day in
     let f =
       if z >= 2299161 then
         (* We use the Num module here to prevent overflow *)
-        let day' = Num.(((num_of_int 4) */ day +/ (num_of_int 274277)) // (num_of_int 146097))
+        let day' = Num.(((num_of_int 4) */ shift_day +/ (num_of_int 274277)) // (num_of_int 146097))
                 |> Num.floor_num
                 |> Num.int_of_num in
         z + 1401 + ((day' * 3) / 4) - 38
-- 
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