/*
datecalc.c
Written 1996/96 by Oliver Kraus
Published by Heinz Heise Verlag 1997 (c't 15/97)
Completly rewritten and put under GPL 2011 by Oliver Kraus
(c) 2011 by Oliver Kraus (olikraus@gmail.com)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
Development goals:
- English version
- Optimized for 8 bit microcontroller
Definitions:
Short Name: y
Long Name: year
Range: 2000...
Short Name: ydn
Long Name: year day number
Range: 1..366
Short Name: cdn
Long Name: century day number
Range: 1...65535
Short Name: ymd
Long Name: Year, Month, Day
Range: 2000...65535, 1..12, 1..31
Conversions
ymd --> y, ydn
get_year_day_number()
y, ydn --> ymd
get_month_by_year_day_number()
get_day_by_year_day_number()
y, ydn --> cdn
to_century_day_number();
cdn --> y, ydn
from_century_day_number();
*/
#include <stdint.h>
/*
Prototype:
uint8_t is_leap_year(uint16_t y)
Description:
Calculate leap year
Arguments:
y year, e.g. 2011 for year 2011
Result:
0 not a leap year
1 leap year
*/
uint8_t is_leap_year(uint16_t y)
{
if (
((y % 4 == 0) && (y % 100 != 0)) ||
(y % 400 == 0)
)
return 1;
return 0;
}
/*
Prototype:
uint16_t get_year_day_number(uint16_t y, uint8_t m, uint8_t d)
Description:
Calculate the day number within a year. 1st of Jan has the number 1.
"Robertson" Algorithm IDAY (CACM Vol 15/#10/Oct 1972)
Arguments:
y year, e.g. 2011 for year 2011
m month with 1 = january to 12 = december
d day starting with 1
Result:
The "day number" within the year: 1 for the 1st of Jan.
See also:
get_month_by_day_number()
*/
uint16_t get_year_day_number(uint16_t y, uint8_t m, uint8_t d)
{
uint8_t tmp1;
uint16_t tmp2;
tmp1 = 0;
if ( m >= 3 )
tmp1++;
tmp2 = m;
tmp2 +=2;
tmp2 *=611;
tmp2 /= 20;
tmp2 += d;
tmp2 -= 91;
tmp1 <<=1;
tmp2 -= tmp1;
if ( tmp1 != 0 )
tmp2 += is_leap_year(y);
return tmp2;
}
/*
Prototype:
uint8_t get_month_by_year_day_number(uint16_t y, uint16_t ydn)
Description:
Get the month from year and day number within a year.
"R. A. Stone" Algorithm (CACM Vol 13/#10/Oct 1970)
Arguments:
y year, e.g. 2011 for year 2011
ydn year day number (1st of Jan has the number 1)
Result:
The month within the year: 1 for January.
See also:
get_year_day_number()
*/
static uint16_t corrected_year_day_number(uint16_t y, uint16_t ydn)
{
uint8_t a;
a = is_leap_year(y);
if ( ydn > 59+a )
{
ydn += 2;
ydn -= a;
}
ydn += 91;
return ydn;
}
uint8_t get_month_by_year_day_number(uint16_t y, uint16_t ydn)
{
uint8_t a;
ydn = corrected_year_day_number(y, ydn);
ydn *= 20;
ydn /= 611;
a = ydn;
a -= 2;
return a;
}
/*
Prototype:
uint8_t get_day_by_year_day_number(uint16_t y, uint16_t ydn)
Description:
Get the day within month from year and day number within a year.
"R. A. Stone" Algorithm (CACM Vol 13/#10/Oct 1970)
Arguments:
y year, e.g. 2011 for year 2011
ydn year day number (1st of Jan has the number 1)
Result:
The day within a month: 1 for the first day of a month.
See also:
get_year_day_number()
*/
uint8_t get_day_by_year_day_number(uint16_t y, uint16_t ydn)
{
uint8_t m;
uint16_t tmp;
m = get_month_by_year_day_number(y, ydn);
m += 2;
ydn = corrected_year_day_number(y, ydn);
tmp = 611;
tmp *= m;
tmp /= 20;
ydn -= tmp;
return ydn;
}
/*
Prototype:
uint8_t get_weekday_by_year_day_number(uint16_t y, uint16_t ydn)
Description:
Get the day within week from year and day number within a year.
"Zeller" Algorithm
https://de.wikisource.org/wiki/Index:Acta_Mathematica_vol._009_(1886)
https://ia801407.us.archive.org/8/items/actamathematica09upps/actamathematica09upps.pdf
Arguments:
y year, e.g. 2011 for year 2011
ydn year day number (1st of Jan has the number 1)
Result:
The day within a week: 0..6 with 0 = Sunday, 1 = Monday, ...
See also:
get_year_day_number()
*/
uint8_t get_weekday_by_year_day_number(uint16_t y, uint16_t ydn)
{
uint8_t j, c, tmp8;
uint16_t tmp16;
y--;
j = y % 100;
c = y / 100;
tmp16 = c;
tmp16 *= 5;
tmp16 += ydn;
tmp8 = j;
j >>= 2;
c >>= 2;
tmp8 += j;
tmp8 += c;
tmp8 += 28;
tmp16 += tmp8;
tmp16 %= 7;
return tmp16;
}
/*
Prototype:
uint16_t to_century_day_number(uint16_t y, uint16_t ydn)
Description:
Calculate days since January, 1st, 2000
Arguments:
y year, e.g. 2011 for year 2011
ydn year day number (1st of Jan has the number 1)
*/
uint16_t to_century_day_number(uint16_t y, uint16_t ydn)
{
uint16_t cdn;
cdn = ydn;
cdn--;
while( y > 2000 )
{
y--;
cdn += 365;
cdn += is_leap_year(y);
}
return cdn;
}
void from_century_day_number(uint16_t cdn, uint16_t *year, uint16_t *ydn)
{
uint16_t y, days_per_year;
y = 2000;
for(;;)
{
days_per_year = 365;
days_per_year += is_leap_year(y);
if ( cdn >= days_per_year )
{
cdn -= days_per_year;
y++;
}
else
break;
}
cdn++;
*year = y;
*ydn = cdn;
}
/*
Calculate the seconds after 2000-01-01 00:00. The largest possible
time is 2136-02-07 06:28:15
*/
uint32_t to_time(uint16_t cdn, uint8_t h, uint8_t m, uint8_t s)
{
uint32_t t;
t = cdn;
t *= 24;
t += h;
t *= 60;
t += m;
t *= 60;
t += s;
return t;
}
void from_time(uint32_t t, uint16_t *cdn, uint8_t *h, uint8_t *m, uint8_t *s)
{
*s = t % 60;
t /= 60;
*m = t % 60;
t /= 60;
*h = t % 24;
t /= 24;
*cdn = t;
}
uint32_t to_sec_since_2000(uint16_t y, uint8_t mo, uint8_t d, uint8_t h, uint8_t mi, uint8_t s)
{
uint16_t ydn = get_year_day_number(y, mo, d);
uint16_t cdn = to_century_day_number(y, ydn);
return to_time(cdn, h, mi, s);
}
/*
Calculate the minutes after 2000-01-01 00:00.
*/
uint32_t to_minutes(uint16_t cdn, uint8_t h, uint8_t m)
{
uint32_t t;
t = cdn;
t *= 24;
t += h;
t *= 60;
t += m;
return t;
}
void from_minutes(uint32_t t, uint16_t *cdn, uint8_t *h, uint8_t *m)
{
*m = t % 60;
t /= 60;
*h = t % 24;
t /= 24;
*cdn = t;
}
uint32_t to_minutes_since_2000(uint16_t y, uint8_t mo, uint8_t d, uint8_t h, uint8_t mi)
{
uint16_t ydn = get_year_day_number(y, mo, d);
uint16_t cdn = to_century_day_number(y, ydn);
return to_minutes(cdn, h, mi);
}
/*
Eingabe: Jahr
Ausgabe: Tagesnummer des Ostersonntag,
rel. zum Jahresanfang.
Algorithmus "Computus ecclesiasticus"
325 n.Chr. wurde Ostern auf den Sonntag nach
dem ersten Fruehlingsvollmond festgelegt. Damit
liegt Ostern zwischen dem 22. Maerz und
dem 25. April.
*/
/*
int ostersonntag(int jahr)
{
int gz, jhd, ksj, korr, so, epakte, n;
gz = (jahr%19)+1;
jhd = jahr/100+1;
ksj = (3*jhd)/4-12;
korr = (8*jhd+5)/25-5;
so = (5*jahr)/4-ksj-10;
epakte = (11*gz+20+korr-ksj) % 30;
if ( (epakte == 25 && gz > 11) || epakte == 24 )
epakte++;
n = 44-epakte;
if ( n < 21 )
n = n + 30;
n = n + 7 - (so+n) % 7;
n += schaltjahr(jahr);
return n+59;
}
*/