Coming from VB6 I found I had a need for Date Functions such as DateAdd (add a number of Days to a Date), DateDiff (calculate the number of Days between 2 Dates) and DayOfWeek for a given Date; so I had a go. Code is below. Any / all constructive criticisms appreciated.
Code: Select all
'
' doogle 23/07/2014
'
dim daystomonth(13,2)
data 0,0,31,31,59,60,90,91,120,121,151,152,181,182,212,213,243,244
data 273,274,304,305,334,335,365,366
for i = 0 to 12
for j = 0 to 1
read daystomonth(i,j)
next j
next i
def datetosecs(d,m,y)
'
' Create a 'Timestamp' representing seconds from 1/1/1900
' ignore leap seconds
' But check the year for leap year so
' February gets dealt with properly
'
if y % 4 = 0 then
thisleap = 1
else
thisleap = 0
end if
if y >= 400 and y % 400 = 0 then
thisleap = 0
end if
days = ((y - 1970) * 365)
mdays = .daystomonth(m-1,thisleap)
ddays = d - 1
totaldays = days + mdays + ddays
totalsecs = totaldays * (24 * 60 * 60)
return totalsecs
end def
def secondstodate$(secs)
'
' Convert 'Timestamp' back to a Date
' Again ignore leap seconds but check the
' resulting year so February is processed properly
'
totaldays = secs / (24 * 60 * 60)
years = floor(totaldays / 365)
daysrem = totaldays - (years * 365)
year = 1970 + years
if year % 4 = 0 then
leap = 1
else
leap = 0
end if
if year >= 400 and year % 400 = 0 then
leap = 0
end if
mfound = -1
if daysrem <> 0 then
do
if daysrem < .daystomonth(i,leap) then
mfound = i
else
i = i + 1
end if
until mfound <> -1
m = mfound
d = daysrem - .daystomonth(m-1, leap) + 1
else
m = 12
d = 31
year = year - 1
end if
d$ = left$("00", 2-len(str$(d))) & str$(d)
m$ = left$("00", 2-len(str$(m))) & str$(m)
y$ = str$(year)
return d$ & "/" & m$ & "/" & y$
end def
def dateadd$(date$,days)
daysecs = days * 24 * 60 * 60
d = val(mid$(date$,0,2))
m = val(mid$(date$,3,2))
y = val(mid$(date$,6,4))
da = datetosecs(d,m,y)
daysecs = da + daysecs
return secondstodate$(daysecs)
end def
def datediff(date1$, date2$)
d = val(mid$(date1$,0,2))
m = val(mid$(date1$,3,2))
y = val(mid$(date1$,6,4))
da1 = datetosecs(d,m,y)
d = val(mid$(date2$,0,2))
m = val(mid$(date2$,3,2))
y = val(mid$(date2$,6,4))
da2 = datetosecs(d,m,y)
dadiff = da1 - da2
return dadiff /(24*60*60)
end def
def dayofweek$(date$)
'
' Uses Zeller's Congruence
' 0 = Saturday,7 = Friday
'
dim days$(7)
for i = 0 to 6
read days$(i)
next i
'
' Expect Date in dd[sep]mm[sep]yyyy format
' where [sep] can be any single character
'
d = val(mid$(date$,0,2))
m = val(mid$(date$,3,2))
y = val(mid$(date$,6,4))
'
'Algorithm requires Jan = month 13 Feb = month 14
'
if m = 1 then m =13
if m = 2 then m = 14
t1 = floor((13*(m+1))/5)
k = y % 100
j = floor(y / 100)
h = (d + t1 + k + floor(k/4) + 5 + (5*j)) % 7
return days$(h)
data "Saturday","Sunday","Monday","Tuesday","Wednesday","Thursday","Friday"
end def
'
' Test Data
'
print "25/07/2014 is a ";dayofweek$("25/07/2014")
print "12/02/2003 + 20 Days is: "; dateadd$("12/02/2003",20)
print "Days difference between 01/03/2004 and 28/02/2004 is "; datediff("01/03/2004","28/02/2004")
print "Days difference between 01/03/2014 and 28/02/2014 is "; datediff("01/03/2014","28/02/2014")
print "20/07/2014 less 10 days is "; dateadd$("20/07/2014",-10)
