ntp_calendar.h   [plain text]

/*
 * ntp_calendar.h - definitions for the calendar time-of-day routine
 */
#ifndef NTP_CALENDAR_H
#define NTP_CALENDAR_H

#include "ntp_types.h"

struct calendar {
	u_short year;		/* year (A.D.) */
	u_short yearday;	/* day of year, 1 = January 1 */
	u_char month;		/* month, 1 = January */
	u_char monthday;	/* day of month */
	u_char hour;		/* hour of day, midnight = 0 */
	u_char minute;		/* minute of hour */
	u_char second;		/* second of minute */
};

/*
 * Days in each month.  30 days hath September...
 */
#define	JAN	31
#define	FEB	28
#define	FEBLEAP	29
#define	MAR	31
#define	APR	30
#define	MAY	31
#define	JUN	30
#define	JUL	31
#define	AUG	31
#define	SEP	30
#define	OCT	31
#define	NOV	30
#define	DEC	31

/*
 * We deal in a 4 year cycle starting at March 1, 1900.  We assume
 * we will only want to deal with dates since then, and not to exceed
 * the rollover day in 2036.
 */
#define	SECSPERMIN	(60)			/* seconds per minute */
#define	MINSPERHR	(60)			/* minutes per hour */
#define	HRSPERDAY	(24)			/* hours per day */
#define	DAYSPERYEAR	(365)			/* days per year */

#define	SECSPERDAY	(SECSPERMIN*MINSPERHR*HRSPERDAY)
#define	SECSPERYEAR	(365 * SECSPERDAY)	/* regular year */
#define	SECSPERLEAPYEAR	(366 * SECSPERDAY)	/* leap year */

#define	MAR1900		((JAN+FEB) * SECSPERDAY) /* no leap year in 1900 */
#define	DAYSPERCYCLE	(365+365+365+366)	/* 3 normal years plus leap */
#define	SECSPERCYCLE	(DAYSPERCYCLE*SECSPERDAY)
#define	YEARSPERCYCLE	4

/*
 * Gross hacks.  I have illicit knowlege that there won't be overflows
 * here, the compiler often can't tell this.
 */
#define	TIMES60(val)	((((val)<<4) - (val))<<2)	/* *(16 - 1) * 4 */
#define	TIMES24(val)	(((val)<<4) + ((val)<<3))	/* *16 + *8 */
#define	TIMES7(val)	(((val)<<3) - (val))		/* *8  - *1 */
#define	TIMESDPERC(val)	(((val)<<10) + ((val)<<8) \
			+ ((val)<<7) + ((val)<<5) \
			+ ((val)<<4) + ((val)<<2) + (val))	/* *big* hack */

/*
 * Another big hack.  Cycle 22 started on March 1, 1988.  This is
 * STARTCYCLE22 seconds after the start of cycle 0.
 */
#define	CYCLE22		(22)
#define	STARTCYCLE22	(u_long)(0xa586b500)	/* 2777068800 */
#define	MAR1988		(u_long)(STARTCYCLE22 + (u_long)MAR1900)

/*
 * The length of January + February in leap and non-leap years.
 */
#define	JANFEBNOLEAP	((JAN+FEB) * SECSPERDAY)
#define	JANFEBLEAP	((JAN+FEBLEAP) * SECSPERDAY)


extern	void	caljulian	(u_long, struct calendar *);
extern	u_long	caltontp	(const struct calendar *);

/*
 * Additional support stuff for Ed Rheingold's calendrical calculations
 */

/*
 * Start day of NTP time as days past the imaginary date 12/1/1 BC.
 * (This is the beginning of the Christian Era, or BCE.)
 */
#define	DAY_NTP_STARTS 693596
/*
 * The Gregorian calendar is based on a 400 year cycle.  This is the number
 * of days in each cycle.
 */
#define	GREGORIAN_CYCLE_DAYS 146097

/*
 * Days in a normal 100 year leap year calendar.  We lose a leap year day
 * in years evenly divisible by 100 but not by 400.
 */
#define	GREGORIAN_NORMAL_CENTURY_DAYS 36524

/*
 * Days in a normal 4 year leap year calendar cycle.
 */
#define	GREGORIAN_NORMAL_LEAP_CYCLE_DAYS 1461

#define	is_leapyear(y)	(!((y) % 4) && !(!((y) % 100) && (y) % 400))

#endif