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From: Roedy Green on 12 Mar 2010 15:42
On Fri, 12 Mar 2010 08:12:03 -0800 (PST), laredotornado
<laredotornado(a)zipmail.com> wrote, quoted or indirectly quoted someone
who said :

>I'm using Java 1.5. I have a java.util.Date object and I would like
>to determine if it's date (i.e. year, month, and day) are greater than
>(in the future) or equal to today's date (year, month, and day).
>However, I don't care about any time component (hour, minute,
>second ...) when the comparison is taking place. What is the easiest
>way I can determine this?

1. use BigDate. see http://mindprod.com/products1.html#BIGDATE

2. extract the long timestamp from each date. Divide by the number of
milliseconds in a day to get days since 1970. Compare those, keeping
in mind these are UTC days. Christmas in Moscow may compare different
from Christmas in Toledo.

for background see http://mindprod.com/jgloss/calendar.html
http://mindprod.com/jgloss/time.html
http://mindprod.com/jgloss/date.html
--
Roedy Green Canadian Mind Products
http://mindprod.com

The first 90% of the code accounts for the first 90% of the development time. The remaining 10% of the code accounts for the other 90% of the development time.
~ Tom Cargill
From: Lew on 12 Mar 2010 16:12
On Mar 12, 11:12 am, laredotornado <laredotorn...(a)zipmail.com> wrote:
> Hi,
>
> I'm using Java 1.5.  I have a java.util.Date object and I would like
> to determine if it's date (i.e. year, month, and day) are greater than
> (in the future) or equal to today's date (year, month, and day).
> However, I don't care about any time component (hour, minute,
> second ...) when the comparison is taking place.  What is the easiest
> way I can determine this?

Use Calendar. Normalize to the same time zone. Zero out the time
portion (using 'set()', *not* 'clear()'!). Compare using 'after()' or
'before()'. Read the Javadocs.

--
Lew

From: Lew on 12 Mar 2010 16:14
Roedy Green wrote:
> 2. extract the long timestamp from each date.  Divide by the number of
> milliseconds in a day to get days since 1970. Compare those, keeping
> in mind these are UTC days. Christmas in Moscow may compare different
> from Christmas in Toledo.

That will have troubles this weekend in my part of the world, i.e.,
give the wrong answer.

The number of milliseconds in a day depends on the date.

--
Lew
From: Roedy Green on 12 Mar 2010 22:07
On Fri, 12 Mar 2010 13:14:11 -0800 (PST), Lew <lew(a)lewscanon.com>
wrote, quoted or indirectly quoted someone who said :

>That will have troubles this weekend in my part of the world, i.e.,
>give the wrong answer.
>
>The number of milliseconds in a day depends on the date.

I have long railed against DST as a nutty idea.
http://mindprod.com/jgloss/dst.html

The Rachael Maddow show trashed it tonight. It turns out it does not
save energy. With the extra evening hours people drive to the mall or
ballpark. It is a retail stimulus and a way to increase gas
consumption.

The story is we do it for the farmers. They strenuously opposed it
when it was introduced. It gave them one less hour before the city
markets opened.

I wonder how many people have been killed by the anomalies when the
time changes. I could imagine some incompetent maker of medical pumps
giving a double dose, or skipping a dose.

I think anyone who has to co-ordinate should be tracking time in UTC.
But even then data entry still happens in local time.
--
Roedy Green Canadian Mind Products
http://mindprod.com

The first 90% of the code accounts for the first 90% of the development time. The remaining 10% of the code accounts for the other 90% of the development time.
~ Tom Cargill
From: Roedy Green on 12 Mar 2010 22:22
On Fri, 12 Mar 2010 12:42:32 -0800, Roedy Green
<see_website(a)mindprod.com.invalid> wrote, quoted or indirectly quoted
someone who said :

>
>1. use BigDate. see http://mindprod.com/products1.html#BIGDATE

BigDate from = new BigDate( 2010, 2, 28);
BigDate to = new BigDate ( 2010, 3, 12 );
int diff = to.compareTo( from );

Or starting with a timestamp in the form of a UTC Date and a TimeZone

BigDate from = new BigDate( dateFrom, tzFrom );
BigDate to = new BigDate ( dateTo, tzTo );
int diff = to.compareTo( from );
--
Roedy Green Canadian Mind Products
http://mindprod.com

The first 90% of the code accounts for the first 90% of the development time. The remaining 10% of the code accounts for the other 90% of the development time.
~ Tom Cargill
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