Rewrite the function that converts timestamp to year, month and day in C++.

src/macros.py

Index: src/macros.py
===================================================================
--- src/macros.py	(revision 4103)
+++ src/macros.py	(working copy)
@@ -136,9 +136,9 @@
 # a type error is thrown.
 macro DATE_VALUE(arg) = (%_ClassOf(arg) === 'Date' ? %_ValueOf(arg) : ThrowDateTypeError());
 macro DAY(time) = ($floor(time / 86400000));
-macro MONTH_FROM_TIME(time) = (FromJulianDay(($floor(time / 86400000)) + 2440588).month);
-macro DATE_FROM_TIME(time) = (FromJulianDay(($floor(time / 86400000)) + 2440588).date);
-macro YEAR_FROM_TIME(time) = (FromJulianDay(($floor(time / 86400000)) + 2440588).year);
+macro MONTH_FROM_TIME(time) = (MonthFromTime(time));
+macro DATE_FROM_TIME(time) = (DateFromTime(time));
+macro YEAR_FROM_TIME(time) = (YearFromTime(time));
 macro HOUR_FROM_TIME(time) = (Modulo($floor(time / 3600000), 24));
 macro MIN_FROM_TIME(time) = (Modulo($floor(time / 60000), 60));
 macro SEC_FROM_TIME(time) = (Modulo($floor(time / 1000), 60));