[gnumeric] Fix WORKDAY with respect to 1900/2/29

[Andreas J. Guelzow <guelzow src gnome org>]

commit e7cd5b8297b0121025d808dd5ab828d1911644c8
Author: Andreas J Guelzow <aguelzow pyrshep ca>
Date:   Sat Jul 3 14:17:10 2010 -0600

    Fix WORKDAY with respect to 1900/2/29
    
    2010-07-03  Andreas J. Guelzow <aguelzow pyrshep ca>
    
    	* functions.c (gnumeric_workday): take care of 1900/2/29

 plugins/fn-date/ChangeLog   |    4 ++++
 plugins/fn-date/functions.c |   33 +++++++++++++++++++++------------
 2 files changed, 25 insertions(+), 12 deletions(-)
---
diff --git a/plugins/fn-date/ChangeLog b/plugins/fn-date/ChangeLog
index e47143d..040ae51 100644
--- a/plugins/fn-date/ChangeLog
+++ b/plugins/fn-date/ChangeLog
@@ -1,5 +1,9 @@
 2010-07-03  Andreas J. Guelzow <aguelzow pyrshep ca>
 
+	* functions.c (gnumeric_workday): take care of 1900/2/29
+
+2010-07-03  Andreas J. Guelzow <aguelzow pyrshep ca>
+
 	* functions.c (help_networkdays): add new argument description
 	(gnumeric_networkdays): implement weekend extension
 	(gnumeric_workday): don't leak under erros
diff --git a/plugins/fn-date/functions.c b/plugins/fn-date/functions.c
index dbb4dd9..452be86 100644
--- a/plugins/fn-date/functions.c
+++ b/plugins/fn-date/functions.c
@@ -842,31 +842,34 @@ gnumeric_workday (GnmFuncEvalInfo *ei, GnmValue const * const *argv)
 
 
 	weekday = g_date_get_weekday (&date);
-	serial = go_date_g_to_serial (&date, conv);
 
 	if (idays > 0) {
 		int h = 0;
+		guint diff = 0;
+		int old_serial;
 
 		weekday = weekday % 7;
 		while (weekends[weekday]) {
 			weekday = (weekday > 0) ? (weekday - 1) : G_DATE_SATURDAY;
-			serial--;
+			diff++;
 		}
+		g_date_subtract_days (&date, diff);
+		old_serial = go_date_g_to_serial (&date, conv);
 
 		while (idays > 0) {
 			int dm_part_week = idays % n_non_weekend;
 			int ds = idays / n_non_weekend * 7;
-			int old_serial = serial;
-			
-			serial += ds;
 
+			g_date_add_days (&date, ds);
+			
 			while (dm_part_week) {
-				serial++;
+				g_date_add_days (&date, 1);
 				weekday = (weekday + 1) % 7;
 				if (!weekends[weekday])
 					dm_part_week--;
 			}
 
+			serial = go_date_g_to_serial (&date, conv);
 			/*
 			 * we may have passed holidays.
 			 */
@@ -876,32 +879,37 @@ gnumeric_workday (GnmFuncEvalInfo *ei, GnmValue const * const *argv)
 					idays++;
 				h++;
 			}
+			old_serial = serial;
 		}
 	} else if (idays < 0) {
 		int h = nholidays - 1;
+		guint diff = 0;
+		int old_serial;
 
 		weekday = weekday % 7;
 		while (weekends[weekday]) {
 			weekday = (weekday + 1) % 7;
-			serial++;
+			diff++;
 		}
+		g_date_add_days (&date, diff);
+		old_serial = go_date_g_to_serial (&date, conv);
 
 		idays = -idays;
 		while (idays > 0) {
 			int dm_part_week = idays % n_non_weekend;
 			int ds = idays / n_non_weekend * 7;
-			int old_serial = serial;
 			
-			serial -= ds;
-
+			g_date_subtract_days (&date, ds);
+			
 			while (dm_part_week) {
-				serial--;
+				g_date_subtract_days (&date, 1);
 				weekday = (weekday > 0) ? (weekday - 1) 
 					: G_DATE_SATURDAY;
 				if (!weekends[weekday])
 					dm_part_week--;
 			}
 			
+			serial = go_date_g_to_serial (&date, conv);
 			/*
 			 * we may have passed holidays.
 			 */
@@ -911,8 +919,9 @@ gnumeric_workday (GnmFuncEvalInfo *ei, GnmValue const * const *argv)
 					idays++;
 				h--;
 			}
+			old_serial = serial;
 		}
-	}
+	} else serial = go_date_g_to_serial (&date, conv);
 
 	if (weekends != default_weekends)
 		g_free (weekends);