Re: Duration Calculation- Use BigDate

Hi
Use this
http://mindprod.com/jgloss/bigdate.html
for all your date calculations works fine DST and all
possible conditions,
Create a BigDate instance of the 2 dates you want to
compare and then do
bigDeciamal2.getOrdinal() - bigDecimal1.getOrdinal();

This would give you number of days difference

Ashish

--- NGay@xxxxxxxxxxxxx wrote:

This is part of the current problem - the date

related classes seem

to be trying to deal with Daylight Savings Time or

something and when

your dates cross the changeover point the results

are inaccurate.

Besides - doesn't it strike you as thoroughly

silly that one should

even have to contemplate "playing" with

milliseconds to get a count

of a number of days! It is insane that such steps

should be required

in a so-called "modern" language.

IHMO one of the problems is the name of the class!
java.util.Date should
be called something like java.util.PointInTime since
it represents a
specific moment, not a complete 24 hour day - and
this would hopefully stop
so many programmers from being initially confused by
how to use it.
There's no actual "date" class which can store a
date without caring what
time of day it is.

Here's the code I wrote for it, and been using this
for a while and have
JUnit tests for it which test all the DST change
scenarios, so I'm pretty
sure it works OK, at least in the way I use it. It
relies on and (mostly)
validates that you only pass it midnight times, so
it wouldn't work with
the example posted using 8am/8pm times.

Hope this helps,

Nigel Gay,
Computer Patent Annuities Limited.

/**
* Counts the number of days between the two
dates, i.e. 2nd date -
1st date; the dates are assumed to have no time
component
* @param firstDate The earlier date
* @param secondDate The later date
* @return The number of days between the two
dates
* @throws IllegalArgumentException If the
dates have a time
component
*/
public static int calcDaysBetweenDates (Date
firstDate, Date
secondDate)
throws IllegalArgumentException
{
// It won't necessarily be an even
number of 24 hours between
the two dates - there might be daylight savings
involved, in which case
// there may be a 23 or 25 hour day in
there somewhere -
however it should be an even number of hours between
the two dates
long difference = secondDate.getTime ()
- firstDate.getTime ();

if (difference < 0)
throw new IllegalArgumentException
("calcDaysBetweenDates: Second date must be equal to
or later than the
first date");

long millisecondsInAnHour = 1000 * 60 *
60;

if (difference % millisecondsInAnHour !=
0)
throw new IllegalArgumentException
("calcDaysBetweenDates: Dates must not have a time
component (1)");

difference = difference /
millisecondsInAnHour;

// We should only stray +/- 1 hour from
regular 24 hour days
long remainder = difference % 24;
if ((remainder != 0) && (remainder != 1)
&& (remainder != 23))
throw new IllegalArgumentException
("calcDaysBetweenDates: Dates must not have a time
component (2)");

// Adjust number of hours to make it an
even 24
if (remainder == 23)
remainder = -1;

difference = (difference - remainder) /
24;

return (int) difference;
}

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