Hi to all!
Sorry if this has already been answered but I couldn't find a related
thread in the archives.
I have an application which makes use of the datediff function to
figure out length of times in days between to dates. In other words,
how many days are there between January 1st and January 31st.
I've ran into a problem with this app. I've used the next piece of
code to reproduce it.
<cfset dtStart = createDate( 2005, 01, 01 )>
<cfloop index="i" from="0" to="365" step="1">
<cfoutput>
#i# dateDiff( 'd', #dtStart#, #dateAdd( 'd', i, dtStart )# ):
#dateDiff( 'd', dtStart, dateAdd( 'd', i, dtStart ) )#<br
/></cfoutput>
</cfloop>
When running this piece of code I would have expected the value of "i"
to always be equal to the result of the dateDiff call... how wrong of
me...
When I run the code, I get this output:
0 dateDiff( 'd', {ts '2005-01-01 00:00:00'}, {ts '2005-01-01 00:00:00'} ): 0
1 dateDiff( 'd', {ts '2005-01-01 00:00:00'}, {ts '2005-01-02 00:00:00'} ): 1
2 dateDiff( 'd', {ts '2005-01-01 00:00:00'}, {ts '2005-01-03 00:00:00'} ): 2
[...]
92 dateDiff( 'd', {ts '2005-01-01 00:00:00'}, {ts '2005-04-03 00:00:00'} ): 92
93 dateDiff( 'd', {ts '2005-01-01 00:00:00'}, {ts '2005-04-04 00:00:00'} ): 92
94 dateDiff( 'd', {ts '2005-01-01 00:00:00'}, {ts '2005-04-05 00:00:00'} ): 93
[...]
301 dateDiff( 'd', {ts '2005-01-01 00:00:00'}, {ts '2005-10-29 00:00:00'} ): 300
302 dateDiff( 'd', {ts '2005-01-01 00:00:00'}, {ts '2005-10-30 00:00:00'} ): 301
303 dateDiff( 'd', {ts '2005-01-01 00:00:00'}, {ts '2005-10-31 00:00:00'} ): 303
[...]
364 dateDiff( 'd', {ts '2005-01-01 00:00:00'}, {ts '2005-12-31 00:00:00'} ): 364
365 dateDiff( 'd', {ts '2005-01-01 00:00:00'}, {ts '2006-01-01 00:00:00'} ): 365
As you can see I seem to loose a day on April 4th and gain it back on
October 31st. On my server's timezone setting (Eastern Standard Time -
GMT+5) these date correspond to the Daylight Saving Time date changes.
I know a day as 24 hours and I can understand why on those days the
difference in hours is 23 and 25 respectively. What I can't undestand
is why the difference in days would be impacted by this. April 4th is
not April 3rd.
Run this code to see what I mean:
<cfoutput>
DST dates for 2005:<br />
dateDiff In Hours: dateDiff( 'h', '2005-04-03', '2005-04-04'
):#dateDiff( 'h', '2005-04-03', '2005-04-04' )#<br />
dateDiff In Days: dateDiff( 'd', '2005-04-03', '2005-04-04'
):#dateDiff( 'd', '2005-04-03', '2005-04-04' )#<br />
dateDiff In Hours : dateDiff( 'h', '2005-10-30', '2005-10-31'
):#dateDiff( 'h', '2005-10-30', '2005-10-31' )#<br />
dateDiff In Days : dateDiff( 'd', '2005-10-30', '2005-10-31'
):#dateDiff( 'd', '2005-10-30', '2005-10-31' )#<br />
</cfoutput>
Which gives this output:
DST dates for 2005:
dateDiff In Hours: dateDiff( 'h', '2005-04-03', '2005-04-04' ):23
dateDiff In Hours: dateDiff( 'd', '2005-04-03', '2005-04-04' ):0
dateDiff In Days : dateDiff( 'h', '2005-10-30', '2005-10-31' ):25
dateDiff In Days : dateDiff( 'd', '2005-10-30', '2005-10-31' ):1
Am I a fool for thinking so? Or is this a bug in the implementation of
the datediff function, probably something to do with rounding?
--
Marc
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|
Logware: a new and convenient web-based time tracking application. Start
tracking and documenting hours spent on a project or with a client with Logware
today. Try it for free with a 15 day trial account.
http://www.houseoffusion.com/banners/view.cfm?bannerid=67
Message: http://www.houseoffusion.com/lists.cfm/link=i:4:191308
Archives: http://www.houseoffusion.com/cf_lists/threads.cfm/4
Subscription: http://www.houseoffusion.com/lists.cfm/link=s:4
Unsubscribe:
http://www.houseoffusion.com/cf_lists/unsubscribe.cfm?user=11502.10531.4
Donations & Support: http://www.houseoffusion.com/tiny.cfm/54
