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29 lines
728 B
C
29 lines
728 B
C
#include <time.h>
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#include <string.h>
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// written by Chris.McDonald@uwa.edu.au
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// PROVIDED WITHOUT MUCH EXPLANATION YET!
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// RETURNS 0=Sun, 1=Mon, .....
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//
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int first_day_of_month(int month, int year)
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{
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struct tm tm;
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// SET ALL FIELDS OF tm TO ZERO TO MAKE SOME FIELDS 'UNKNOWN'
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memset(&tm, 0, sizeof(tm));
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// INITIALIZE THE FILEDS THAT WE ALREADY KNOW
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tm.tm_mday = 1;
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tm.tm_mon = month-1; // 0=Jan, 1=Feb, ....
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tm.tm_year = year-1900;
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// ASK THE POSIX FUNCTION mktime TO DETERMINE THE 'UNKNOWN' FIELDS
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// See: http://pubs.opengroup.org/onlinepubs/9699919799/
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mktime(&tm);
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// RETURN THE INTEGER MONTH VALUE
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return tm.tm_wday; // 0=Sun, 1=Mon, .....
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}
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