Merge to XFA: Fix JS seconds since epoch to date conversions.

BUG=515137,564736
TBR=ochang@chromium.org, tsepez@chromium.org

Review URL: https://codereview.chromium.org/1533233002 .
Review URL: https://codereview.chromium.org/1544493003 .

(cherry picked from commit b426e3edde040089b70d1a223c83b90957aa571d)
(cherry picked from commit bd35d484a4027775f19ff93e9143e0b270133d42)

Review URL: https://codereview.chromium.org/1546443002 .

1 files changed, 3 insertions, 3 deletions

diff --git a/fpdfsdk/src/javascript/JS_Value.cpp b/fpdfsdk/src/javascript/JS_Value.cpp
index ea7bfda57a..bd00adcf49 100644
--- a/fpdfsdk/src/javascript/JS_Value.cpp
+++ b/fpdfsdk/src/javascript/JS_Value.cpp
@@ -649,7 +649,7 @@ int _DayFromYear(int y) {
 }
 
 double _TimeFromYear(int y) {
-  return ((double)86400000) * _DayFromYear(y);
+  return 86400000.0 * _DayFromYear(y);
 }
 
 double _TimeFromYearMonth(int y, int m) {
@@ -669,12 +669,12 @@ int _Day(double t) {
 
 int _YearFromTime(double t) {
   // estimate the time.
-  int y = 1970 + (int)(t / (365.0 * 86400000));
+  int y = 1970 + static_cast<int>(t / (365.2425 * 86400000));
   if (_TimeFromYear(y) <= t) {
     while (_TimeFromYear(y + 1) <= t)
       y++;
   } else
-    while (_TimeFromYear(y - 1) > t)
+    while (_TimeFromYear(y) > t)
       y--;
   return y;
 }