usr/src/sys/tahoe/include/clock.h

/*
 * Copyright (c) 1988 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 *      @(#)clock.h     7.2 (Berkeley) %G%
 */

#define SECDAY          ((unsigned)(24*60*60))          /* seconds per day */
#define SECYR           ((unsigned)(365*SECDAY))        /* per common year */

#define YRREF           1970
#define LEAPYEAR(year)  ((year)%4==0)   /* good till time becomes negative */

/*
 * Software clock is software interrupt level 8
 */
#define setsoftclock()  mtpr(SIRR, 0x8)

/*
 * To calculate value for interval timer register, we
 * use the fact that 20512 yields a 60hz clock.
 */
#define hztocount(v)    ((20512*60) / (v))