::: Area #157 (comp.sys.acorn.programmer)
Message: #29456 (Read 16 times, has 0 replies, 2072 bytes)
Date   : Sat Feb 28 01:44:14 1998
From   : Jonathan Graham Harston of fidonet#2:254/27
To     : All
Subject: Re: Calculating dates

> Can anyone advise me as to finding the number of days between two dates?
> I have the dates in the form of 3 integers (day, month and year).

> I have tried with territory manager, but can't get any further than the
> difference between the two in UTC format, and this in itself is a bit (a
> lot) of a hack :-/

[I may be delayed in replying, I've been wading through the treacle
Matthias has been sending]

Call the following function with:

days%=FNDaysSince(TodaysDate,TodaysMonth,TodaysYear,PastDay,PastMonth,Past
Year)

REM Return number of days since a past date
REM Needs: num%=> buffer at least 28 bytes
	    utc%=> buffer at least 5 bytes
DEFFNDaysSince(td%,tm%,ty%,pd%,pm%,py%):LOCAL past%
num%!0=0:num%!4=0:num%!8=0:num%!12=0:REM cs, sec, min, hour
num%!16=td%:num%!20=tm%:num%!24=ty%: REM this date, month, year
SYS "Territory_ConvertOrdinalsToTime",-1,utc%,num%:past%=utc%!1
num%!0=0:num%!4=0:num%!8=0:num%!12=0:REM cs, sec, min, hour
num%!16=pd%:num%!20=pm%:num%!24=py%: REM past date, month, year
SYS "Territory_ConvertOrdinalsToTime",-1,utc%,num%:=(utc%!1-past%)DIV&83D6
:

...or even:
:
REM Convert time and date to 5-byte centi-second count since 1st Jan 1900
DEFPROCConvDate(mem%,d%,m%,y%,hr%,mn%,sc%,cs%):IFy%<100:y%=y%+1900
y%=y%MOD400
d%=y%*365.25+m%*30+d%+VALMID$("120112234455",m%,1)+((y%MOD4)=0)
d%=d%-((y%-1)DIV100)-(m%>2AND((y%MOD4)=0AND(y%MOD100)<>0ORy%=0))+36493
IFd%>146096:d%=d%-146097
d%=d%*&41EB:mem%!1=d%+d%:d%=((hr%*60+mn%)*60+sc%)*100+cs%
?mem%=d%:mem%!1=mem%!1+d%DIV256:ENDPROC
:
REM Return number of days since a past date
REM Needs: ctrl%>=5 bytes
DEFFNDaysSince(td%,tm%,ty%,pd%,pm%,py%):LOCAL past%
PROCConvDate(ctrl%,pd%,pm%,py%,0,0,0,0):past%=ctrl%!1
PROCConvDate(ctrl%,td%,tm%,ty%,0,0,0,0):=(ctrl%!1-past%)DIV&83D6
:

J.G.Harston (JGH BBC PD Library) <mailto: jgh@arcade.demon.co.uk>
70 Camm Street, Walkley, SHEFFIELD S6 3TR
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