php check for a valid date, weird date conversions - php

Question

Is there a way to check to see if a date/time is valid you would think these would be easy to check:
$date = '0000-00-00';
$time = '00:00:00';
$dateTime = $date . ' ' . $time;
if(strtotime($dateTime)) {
// why is this valid?
}
what really gets me is this:
echo date('Y-m-d', strtotime($date));
results in: "1999-11-30",
huh? i went from 0000-00-00 to 1999-11-30 ???
I know i could do comparison to see if the date is either of those values is equal to the date i have but it isn't a very robust way to check. Is there a good way to check to see if i have a valid date? Anyone have a good function to check this?
Edit:
People are asking what i'm running:
Running PHP 5.2.5 (cli) (built: Jul 23 2008 11:32:27) on Linux localhost 2.6.18-53.1.14.el5 #1 SMP Wed Mar 5 11:36:49 EST 2008 i686 i686 i386 GNU/Linux

Answer 1

From php.net
<?php
function isValidDateTime($dateTime)
{
if (preg_match("/^(\d{4})-(\d{2})-(\d{2}) ([01][0-9]|2[0-3]):([0-5][0-9]):([0-5][0-9])$/", $dateTime, $matches)) {
if (checkdate($matches[2], $matches[3], $matches[1])) {
return true;
}
}
return false;
}
?>

Answer 2

As mentioned here: https://bugs.php.net/bug.php?id=45647
There is no bug here, 00-00-00 means 2000-00-00, which is 1999-12-00,
which is 1999-11-30. No bug, perfectly normal.
And as shown with a few tests, rolling backwards is expected behavior, if a little unsettling:
>> date('Y-m-d', strtotime('2012-03-00'))
string: '2012-02-29'
>> date('Y-m-d', strtotime('2012-02-00'))
string: '2012-01-31'
>> date('Y-m-d', strtotime('2012-01-00'))
string: '2011-12-31'
>> date('Y-m-d', strtotime('2012-00-00'))
string: '2011-11-30'

Answer 3

echo date('Y-m-d', strtotime($date));
results in: "1999-11-30"
The result of strtotime is 943920000 - this is the number of seconds, roughly, between the Unix epoch (base from which time is measured) to 1999-11-30.
There is a documented mysql bug on mktime(), localtime(), strtotime() all returning this odd value when you try a pre-epoch time (including "0000-00-00 00:00:00"). There's some debate on the linked thread as to whether this is actually a bug:
Since the time stamp is started from 1970, I don't think it supposed to
work in anyways.
Below is a function that I use for converting dateTimes such as the above to a timestamp for comparisons, etc, which may be of some use to you, for dates beyond "0000-00-00 00:00:00"
/**
* Converts strings of the format "YYYY-MM-DD HH:MM:SS" into php dates
*/
function convert_date_string($date_string)
{
list($date, $time) = explode(" ", $date_string);
list($hours, $minutes, $seconds) = explode(":", $time);
list($year, $month, $day) = explode("-", $date);
return mktime($hours, $minutes, $seconds, $month, $day, $year);
}

Answer 4

Don't expect coherent results when you're out of range:
cf strtotime
cf Gnu Calendar-date-items.html
"For numeric months, the ISO 8601
format ‘year-month-day’ is allowed,
where year is any positive number,
month is a number between 01
and 12, and day is a
number between 01 and 31. A
leading zero must be present if a
number is less than ten."
So '0000-00-00' gives weird results, that's logical!
"Additionally, not all
platforms support negative timestamps,
therefore your date range may be
limited to no earlier than the Unix
epoch. This means that e.g.
%e, %T, %R and %D (there might be
more) and dates prior to Jan
1, 1970 will not work on Windows, some
Linux distributions, and a few other
operating systems."
cf strftime
Use checkdate function instead (more robust):
month:
The month is between 1 and 12 inclusive.
day:
The day is within the allowed number of days for the given
month. Leap year s are taken
into consideration.
year:
The year is between 1 and 32767 inclusive.

Answer 5

This version allows for the field to be empty, has dates in mm/dd/yy or mm/dd/yyyy format, allow for single digit hours, adds optional am/pm, and corrects some subtle flaws in the time match.
Still allows some pathological times like '23:14 AM'.
function isValidDateTime($dateTime) {
if (trim($dateTime) == '') {
return true;
}
if (preg_match('/^(\d{1,2})\/(\d{1,2})\/(\d{2,4})(\s+(([01]?[0-9])|(2[0-3]))(:[0-5][0-9]){0,2}(\s+(am|pm))?)?$/i', $dateTime, $matches)) {
list($all,$mm,$dd,$year) = $matches;
if ($year <= 99) {
$year += 2000;
}
return checkdate($mm, $dd, $year);
}
return false;
}

Answer 6

If you just want to handle a date conversion without the time for a mysql date field, you can modify this great code as I did.
On my version of PHP without performing this function I get "0000-00-00" every time. Annoying.
function ConvertDateString ($DateString)
{
list($year, $month, $day) = explode("-", $DateString);
return date ("Y-m-d, mktime (0, 0, 0, $month, $day, $year));
}

Answer 7

<?php
function is_valid_date($user_date=false, $valid_date = "1900-01-01") {
$user_date = date("Y-m-d H:i:s",strtotime($user_date));
return strtotime($user_date) >= strtotime($valid_date) ? true : false;
}
echo is_valid_date("00-00-00") ? 1 : 0; // return 0
echo is_valid_date("3/5/2011") ? 1 : 0; // return 1

Answer 8

I have been just changing the martin answer above, which will validate any type of date and return in the format you like.
Just change the format by editing below line of script
strftime("10-10-2012", strtotime($dt));
<?php
echo is_date("13/04/10");
function is_date( $str ) {
$flag = strpos($str, '/');
if(intval($flag)<=0){
$stamp = strtotime( $str );
} else {
list($d, $m, $y) = explode('/', $str);
$stamp = strtotime("$d-$m-$y");
}
//var_dump($stamp) ;
if (!is_numeric($stamp)) {
//echo "ho" ;
return "not a date" ;
}
$month = date( 'n', $stamp ); // use n to get date in correct format
$day = date( 'd', $stamp );
$year = date( 'Y', $stamp );
if (checkdate($month, $day, $year)) {
$dt = "$year-$month-$day" ;
return strftime("%d-%b-%Y", strtotime($dt));
//return TRUE;
} else {
return "not a date" ;
}
}
?>

Answer 9

I have used the following code to validate dates coming from ExtJS applications.
function check_sql_date_format($date) {
$date = substr($date, 0, 10);
list($year, $month, $day) = explode('-', $date);
if (!is_numeric($year) || !is_numeric($month) || !is_numeric($day)) {
return false;
}
return checkdate($month, $day, $year);
}

Answer 10

<?php
function is_date( $str ) {
$stamp = strtotime( $str );
if (!is_numeric($stamp)) {
return FALSE;
}
$month = date( 'm', $stamp );
$day = date( 'd', $stamp );
$year = date( 'Y', $stamp );
if (checkdate($month, $day, $year)) {
return TRUE;
}
return FALSE;
}
?>