Greetings. I made this change in two stages hence two commits, but I
think it makes more sense to combine them into one commit.
Unfortunately, I am not a master of git and I don't know how. I can use
git diff to combine the changes, but git format-patch wants to do one
patch per commit.
It is attached.
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or over the web
From 715bf6068f98089a03ca2beb38facbe568ac07ff Mon Sep 17 00:00:00 2001
From: Greg Reagle <greg.rea...@umbc.edu>
Date: Thu, 8 Jan 2015 17:16:19 -0500
Subject: [PATCH 1/2] Julian when month is Sep 1752 or before. Gregorian when
month is Oct 1752 or after.
---
cal.1 | 1 +
cal.c | 22 +++++++++++++++++-----
2 files changed, 18 insertions(+), 5 deletions(-)
diff --git a/cal.1 b/cal.1
index c215340..659d46a 100644
--- a/cal.1
+++ b/cal.1
@@ -28,6 +28,7 @@ of calendars side by side. Each row of calendars contains at most
.IR columns
number of calendars. The defaults are obtained using
.IR localtime (3).
+The Julian calendar is used for Septmeber 1752 and before. Starting with October 1752, the Gregorian calendar is used.
.SH OPTIONS
.TP
.B \-1
diff --git a/cal.c b/cal.c
index 53c6022..a000843 100644
--- a/cal.c
+++ b/cal.c
@@ -5,6 +5,9 @@
#include "util.h"
+enum caltype {Julian, Gregorian};
+enum {Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec};
+
static int
isleap(int year)
{
@@ -19,27 +22,36 @@ static int
monthlength(int year, int month)
{
int mdays[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
- return (month==1 && isleap(year)) ? 29 : mdays[month];
+ return (month==Feb && isleap(year)) ? 29 : mdays[month];
}
/* From http://www.tondering.dk/claus/cal/chrweek.php#calcdow */
static int
-dayofweek(int year, int month, int dom)
+dayofweek(int year, int month, int dom, enum caltype cal)
{
int m, y, a;
month += 1; /* in this formula, 1 <= month <= 12 */
a = (14 - month) / 12;
y = year - a;
m = month + 12*a - 2;
- return (dom + y + y/4 - y/100 + y/400 +((31*m)/12)) % 7;
+
+ if (cal == Gregorian)
+ return (dom + y + y/4 - y/100 + y/400 + (31*m)/12) % 7;
+ else /* cal == Julian */
+ return (5 + dom + y + y/4 + (31*m)/12) % 7;
}
static void
printgrid(int year, int month, int fday, int line)
{
- int dom, offset, d=0;
+ enum caltype cal, offset, dom, d=0;
+
+ if (year < 1752 || (year == 1752 && month <= Sep))
+ cal = Julian;
+ else
+ cal = Gregorian;
+ offset = dayofweek(year, month, 1, cal) - fday;
- offset = dayofweek(year, month, 1) - fday;
if (offset < 0)
offset += 7;
if (line==1) {
--
2.2.1
From 3520c5cccb9958a056e4885108060bdf8ed03526 Mon Sep 17 00:00:00 2001
From: Greg Reagle <greg.rea...@umbc.edu>
Date: Tue, 13 Jan 2015 12:37:30 -0500
Subject: [PATCH 2/2] Using the Julian calendar for dates through September 2,
1752 and the Gregorian calendar for dates from September 14, 1752.
---
cal.1 | 4 +++-
cal.c | 39 ++++++++++++++++++++++++++-------------
2 files changed, 29 insertions(+), 14 deletions(-)
diff --git a/cal.1 b/cal.1
index 659d46a..8619460 100644
--- a/cal.1
+++ b/cal.1
@@ -28,7 +28,7 @@ of calendars side by side. Each row of calendars contains at most
.IR columns
number of calendars. The defaults are obtained using
.IR localtime (3).
-The Julian calendar is used for Septmeber 1752 and before. Starting with October 1752, the Gregorian calendar is used.
+The Julian calendar is used through Sep 2, 1752, and the Gregorian calendar is used starting the next day with Sep 14, 1752.
.SH OPTIONS
.TP
.B \-1
@@ -58,3 +58,5 @@ Specify the first day of the week. 0 is Sunday and 6 is Saturday.
Specify the number months to print. The default is 1.
.SH SEE ALSO
.IR localtime (3)
+.SH STANDARDS
+This program tries to conform to IEEE Std 1003.1, 2013 Edition, q.v. http://pubs.opengroup.org/onlinepubs/9699919799/utilities/cal.html.
diff --git a/cal.c b/cal.c
index a000843..a493ec9 100644
--- a/cal.c
+++ b/cal.c
@@ -5,24 +5,30 @@
#include "util.h"
-enum caltype {Julian, Gregorian};
enum {Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec};
+enum caltype {Julian, Gregorian};
+enum {TRANS_YEAR = 1752, TRANS_MONTH = Sep, TRANS_DAY = 2};
static int
-isleap(int year)
+isleap(int year, enum caltype cal)
{
- if (year % 400 == 0)
- return 1;
- if (year % 100 == 0)
- return 0;
- return (year % 4 == 0);
+ if (cal == Gregorian) {
+ if (year % 400 == 0)
+ return 1;
+ if (year % 100 == 0)
+ return 0;
+ return (year % 4 == 0);
+ }
+ else { /* cal == Julian */
+ return (year % 4 == 0);
+ }
}
static int
-monthlength(int year, int month)
+monthlength(int year, int month, enum caltype cal)
{
int mdays[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
- return (month==Feb && isleap(year)) ? 29 : mdays[month];
+ return (month==Feb && isleap(year,cal)) ? 29 : mdays[month];
}
/* From http://www.tondering.dk/claus/cal/chrweek.php#calcdow */
@@ -44,14 +50,16 @@ dayofweek(int year, int month, int dom, enum caltype cal)
static void
printgrid(int year, int month, int fday, int line)
{
- enum caltype cal, offset, dom, d=0;
+ enum caltype cal;
+ int trans; /* are we in the transition from Julian to Gregorian? */
+ int offset, dom, d=0;
- if (year < 1752 || (year == 1752 && month <= Sep))
+ if (year < TRANS_YEAR || (year == TRANS_YEAR && month <= TRANS_MONTH))
cal = Julian;
else
cal = Gregorian;
+ trans = (year == TRANS_YEAR && month == TRANS_MONTH);
offset = dayofweek(year, month, 1, cal) - fday;
-
if (offset < 0)
offset += 7;
if (line==1) {
@@ -60,9 +68,14 @@ printgrid(int year, int month, int fday, int line)
dom = 1;
} else {
dom = 8-offset + (line-2)*7;
+ if (trans && !(line==2 && fday==3))
+ dom += 11;
}
- for ( ; d < 7 && dom <= monthlength(year, month); ++d, ++dom)
+ for ( ; d < 7 && dom <= monthlength(year, month, cal); ++d, ++dom) {
printf("%2d ", dom);
+ if (trans && dom==TRANS_DAY)
+ dom += 11;
+ }
for ( ; d < 7; ++d)
printf(" ");
}
--
2.2.1
