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Re: determining the difference between two dateTimes

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bill wrote:
> In a scheduling program I need to check to see if there is a conflict 
> between an existing appointment and one that is to be entered.  I 
> figured that I would use dateTime::diff
> 
> the existing appointment is returned as $row['apptTime'], the appt being 
> tested is $dateTM
> 
> $TAptEnd = $dateTM->add(new DateInterval('PT' . $duration .'M'));
> 
> $date = new DateTime($row['apptTime']);  //dateTime object
>        of the beginning of the next appt
> $diff = $date->diff($TAptEnd,true); //difference between
>      the beginning of an existing appt and the end of
>      the  testing.
> 
> if ($diff->format('%i') <0 ) return 1;
> 
> I am running into several problems that suggest that this is not the 
> best way to go about this.
> 
> 1: if the next appointment is the next day I am getting only the time 
> difference between the appointments, eg 10 min, not the whole time.  I 
> would expect the difference to be 24 * 60 + 10, not just the 10.
> 
> 2: if I need to use the day + hours + minutes it gets really messy.
> 
> Suggestions please.
> 
> bill
Convert the whole lot using appropriate calls to remove all daylight 
savings time, into seconds since Jan 1 1970..i.e.. UNIXTIME.

That will give you absolute offset in seconds.

If you are pulling the date times out of MySQL, the call

"set time_zone= '+00:00'"

means that any dates returned for the rest of the session will be UTC.

The the mysql function unix_timestamp(timestamp) will return the number 
of seconds since Jan 1 1970.

If OTOH you are using some other means than an SQL database to store 
times, I suggest you scrap them and use that particular way of 
expressing times and dates. Its very easy to convert from that to the 
local date in any form you want, using a variety of available functions 
in PHP and or C or Mysql.. and you have a simple way of calculating date 
offsets by subtracting two times, and divinding them by 60 - integer or 
floating point - to get the number of minutes apart.

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determining the difference between two dateTimes bill <nobody@spamcop.net> - 2011-06-06 10:47 -0400
  Re: determining the difference between two dateTimes The Natural Philosopher <tnp@invalid.invalid> - 2011-06-06 17:00 +0100
  Re: determining the difference between two dateTimes Jerry Stuckle <jstucklex@attglobal.net> - 2011-06-06 13:58 -0400
    Re: determining the difference between two dateTimes bill <nobody@spamcop.net> - 2011-06-07 06:45 -0400

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