'===========================================================================
' Subject: DATE MODIFYING PROCEDURES          Date: 11-11-97 (11:43)       
'  Author: Hauke Daempfling                   Code: QB, QBasic, PDS        
'  Origin: hcd@berlin.snafu.de              Packet: DATETIME.ABC
'===========================================================================
TYPE DateType
  Day AS INTEGER
  Month AS INTEGER
  Year AS INTEGER
END TYPE

' by Hauke Daempfling
' hcd@berlin.snafu.de
'
'(c)1996 Hauke Daempfling
'
' Give me credit if used!... thanx! :)
'
' Date-modifiying procedures:
' ValidDate: returns -1 if the Date (of DateType) is valid
' DateString: convert DateType back to string format
' DaysPerMonth: returns the number of days in a certain month
' AddDays: adds days to a DateType, keeps months & years "in mind"
' ReadDate: convert a date string (QB DATE$ variable!) to a DateType

DEFINT A-Z
SUB AddDays (Date AS DateType, Days AS INTEGER)
Date.Day = Date.Day + Days
AddDaysCheckThis:
IF Date.Day > DaysPerMonth(Date.Month) THEN
  Date.Day = Date.Day - DaysPerMonth(Date.Month)
  Date.Month = Date.Month + 1
  GOTO AddDaysCheckThis
END IF
IF Date.Month > 12 THEN
  Date.Month = Date.Month - 12
  Date.Year = Date.Year + 1
  GOTO AddDaysCheckThis
END IF
END SUB

FUNCTION DateString$ (Date AS DateType)
  x$ = LTRIM$(RTRIM$(STR$(Date.Month)))
  m$ = "00"
  MID$(m$, 3 - LEN(x$)) = x$
  x$ = LTRIM$(RTRIM$(STR$(Date.Day)))
  d$ = "00"
  MID$(d$, 3 - LEN(x$)) = x$
  x$ = LTRIM$(RTRIM$(STR$(Date.Year)))
  y$ = "0000"
  MID$(y$, 5 - LEN(x$)) = x$
  DateString$ = m$ + "-" + d$ + "-" + y$
END FUNCTION

FUNCTION DaysPerMonth (Month AS INTEGER)
SELECT CASE Month
  CASE 1, 3, 5, 7, 8, 10, 12
    d = 31
  CASE 4, 6, 9, 11
    d = 30
  CASE 2
    d = 28
  CASE ELSE
    d = 30
END SELECT
DaysPerMonth = d
END FUNCTION

SUB ReadDate (DateStr$, Date AS DateType)
Date.Month = VAL(MID$(DateStr$, 1, 2))
Date.Day = VAL(MID$(DateStr$, 4, 2))
Date.Year = VAL(MID$(DateStr$, 7, 4))
END SUB

FUNCTION ValidDate (Date AS DateType)
IF Date.Month < 1 OR Date.Month > 12 THEN EXIT FUNCTION
IF Date.Day < 1 OR Date.Day > DaysPerMonth(Date.Month) THEN EXIT FUNCTION
IF Date.Year < 1 OR Date.Year > 9999 THEN EXIT FUNCTION
ValidDate = -1
END FUNCTION