/* NOTE:  sd_init () is called automatically. */

OPT TURBO

/* Holds a julian date.  These are easiest to perform calculations with. */
OBJECT sd_julianDateType
  year, day
ENDOBJECT

DEF sd_month_BeginDay=NIL,  /* Day of year that month starts on. */
    sd_monthName[12]:ARRAY OF LONG  /* String values for months.       */

PROC sd_isLeapYear(year) RETURN (Mod(year, 4)=0)

PROC sd_init()
  sd_month_BeginDay:=[  1,  32,  60,  91, 121, 152,
                      182, 213, 244, 274, 305, 335]
  sd_monthName[ 0]:='January'
  sd_monthName[ 1]:='February'
  sd_monthName[ 2]:='March'
  sd_monthName[ 3]:='April'
  sd_monthName[ 4]:='May'
  sd_monthName[ 5]:='June'
  sd_monthName[ 6]:='July'
  sd_monthName[ 7]:='August'
  sd_monthName[ 8]:='September'
  sd_monthName[ 9]:='October'
  sd_monthName[10]:='November'
  sd_monthName[11]:='December'
ENDPROC
  /* sd_init */

PROC sd_monthFrom(julianDate:PTR TO sd_julianDateType)
  DEF day, m
  IF sd_month_BeginDay=NIL THEN sd_init()
  day:=julianDate.day
  IF day<Long(sd_month_BeginDay+4) THEN RETURN 1
  IF sd_isLeapYear(julianDate.year) THEN DEC day
  FOR m:=2 TO 11 DO IF day<Long(sd_month_BeginDay+(Mul(m, 4))) THEN RETURN m
ENDPROC m
  /* sd_monthFrom */

PROC sd_monthNameFor(monthNumber) RETURN sd_monthName[monthNumber-1]
  /* Month number must be 1-12.  Can be gotten via sd_monthFrom(). */

PROC sd_dayOfMonthFrom(julianDate:PTR TO sd_julianDateType)
  /* Variables used here for readability. */
  DEF today, month, month_BeginDay, leapYearAdjustment=0
  today:=julianDate.day
  month:=sd_monthFrom(julianDate)
  month_BeginDay:=Long(sd_month_BeginDay+Mul((month-1),4))
  IF (sd_isLeapYear(julianDate.year)) AND (month>2) THEN DEC leapYearAdjustment
  RETURN (today-month_BeginDay+1+leapYearAdjustment)
ENDPROC
  /* sd_dayOfMonthFrom */

PROC sd_add(julianDate:PTR TO sd_julianDateType, numberOfDays)
  /* Add any number of days (within reason) to a julian date. Returns the */
  /* computed julian date.  The parameter julianDate is unmodified.       */
  DEF computedJulianDate:sd_julianDateType, newNumberOfDays
  IF sd_month_BeginDay=NIL THEN sd_init()
  IF ((sd_isLeapYear(julianDate.year)=FALSE) AND
      (julianDate.day+numberOfDays<=365)) OR
     ((sd_isLeapYear(julianDate.year)) AND
      (julianDate.day+numberOfDays<=365))
    computedJulianDate.year:=julianDate.year
    computedJulianDate.day:=julianDate.day+numberOfDays
  ELSE
    computedJulianDate.year:=julianDate.year+1
    computedJulianDate.day:=1;
    IF sd_isLeapYear(julianDate.year)=FALSE
      newNumberOfDays:=numberOfDays-(365-julianDate.day+1)
    ELSE
      newNumberOfDays:=numberOfDays-(366-julianDate.day+1)
    ENDIF
    RETURN sd_add(computedJulianDate, newNumberOfDays)
  ENDIF
ENDPROC computedJulianDate
  /* sd_add */

PROC sd_getCurrentDate(julianDate:PTR TO sd_julianDateType)
/* Parameter julianDate must not be NIL! */
  DEF ds:datestamp, baseDate:sd_julianDateType, currentDate:PTR TO sd_julianDateType
  DateStamp(ds)
  baseDate.year:=1978  /* All dates are derived from this year. */
  baseDate.day:=1      /* 1 January (julian format).            */
  currentDate:=sd_add(baseDate, ds.days)
  julianDate.year:=currentDate.year
  julianDate.day:=currentDate.day
ENDPROC julianDate
  /* sd_getCurrentDate */