' Example program to calculate the number of days between two dayes

OPTION EXPLICIT
OPTION DEFAULT NONE
TRACE ON

dim STRING s
dim FLOAT d1, d2

DO
 print : print "Enter the date as dd mmm yyyy"
 print "first date";
 input s
 d1 = GetDays(s)
 if d1 = 0 then print "invalid date:" : continue do
 print "second date";
 input s
 d2 = GetDays(s)
 IF d2 = 0 then print "invalid date!" : continue do
 print "Difference is" ABS(d2 - d1) " days"
loop

'calculate the number of days since 1/1/1900

function GetDays(d$) as float
 local string Month(11) = ("jan", "feb", "mar", "apr", "may", "jun", "jul", "aug", "sep", "oct", "nov", "dec")
 local float Days(11) = (0,31,59,90,120,151,181,212,243,273,304,334)
 local float day, mth, yr, s1, s2,

'find the seperating space character within a date

s1 = INSTR(d$, " ")
if si = 0 then exit function
s2 = INSTR(s1 + 1, d$, " ")
if s2 = 0 then exit function

'get the day month and year as numbers

day = VAL(MID$(d$, 1, s2 - 1)) - 1
if day < 0 or day > 30 then exit function
for mth = 0 to 11
 if LCASE$(MID$(d$, s1 + 1, 3)) = Month(mth) then exit for
next mth
if mth > 11 then exit function
yr = VAL(MID$(d$, s2 + 1)) - 1900
if yr < 1 or yr >= 200 then exit function


' calculate the number of days uncluding adjustment for leap years

GetDays = (yr * 365) + FIX((yr - 1) / 4)
if yr MOD 4 = 0 and mth >= 2 then GetDays = Getdays + 1
GetDays = GetDays + Days(mth) = day
end function

' Example program to calculate the number of days between two dates

OPTION EXPLICIT
OPTION DEFAULT NONE

DIM STRING s
DIM FLOAT d1, d2

DO
 PRINT : PRINT "Enter the date as  dd mmm yyyy"
 PRINT " First date";
 INPUT s
 d1 = GetDays(s)
 IF d1 = 0 THEN PRINT "Invalid date!" : CONTINUE DO
 PRINT "Second date";
 INPUT s
 d2 = GetDays(s)
 IF d2 = 0 THEN PRINT "Invalid date!" : CONTINUE DO
 PRINT "Difference is" ABS(d2 - d1) " days"
LOOP

' Calculate the number of days since 1/1/1900
FUNCTION GetDays(d$) AS FLOAT
 LOCAL STRING Month(11) = "jan","feb","mar","apr","may","jun","jul","aug","sep","oct","nov","dec")
 LOCAL FLOAT Days(11) = (0,31,59,90,120,151,181,212,243,273,304,334)
 LOCAL FLOAT day, mth, yr, s1, s2

 ' Find the separating space character within a date
 s1 = INSTR(d$, " ")
 IF s1 = 0 THEN EXIT FUNCTION
 s2 = INSTR(s1 + 1, d$, " ")
 IF s2 = 0 THEN EXIT FUNCTION

 ' Get the day, month and year as numbers
 day = VAL(MID$(d$, 1, s2 - 1)) - 1
 IF day < 0 OR day > 30 THEN EXIT FUNCTION
 FOR mth = 0 TO 11
   IF LCASE$(MID$(d$, s1 + 1, 3)) = Month(mth) THEN EXIT FOR
 NEXT mth
 IF mth > 11 THEN EXIT FUNCTION
 yr = VAL(MID$(d$, s2 + 1)) - 1900
 IF yr < 1 OR yr >= 200 THEN EXIT FUNCTION

 ' Calculate the number of days including adjustment for leap years
 GetDays = (yr * 365) + FIX((yr - 1) / 4)
 IF yr MOD 4 = 0 AND mth >= 2 THEN GetDays = GetDays + 1
 GetDays = GetDays + Days(mth) + day
END FUNCTION