I have this code, and it prints out as '01/01/1970'
$dob = mktime(0, 0, 0, date("m"), date("d")-1, date("y")-18);
echo "DOB is ".date("d/m/y", $dob);
Why is the year not 18 years less than today?
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Try it on writecodeonline.com/php (It gives 15/09/03. As if you used "Y". Weird. Ideone and codepad give 01/01/70.)Ray Toal– Ray Toal2011-09-16 08:09:28 +00:00Commented Sep 16, 2011 at 8:09
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@Ray Toal: or codepad.orgMD Sayem Ahmed– MD Sayem Ahmed2011-09-16 08:13:38 +00:00Commented Sep 16, 2011 at 8:13
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@Sayem Edited the comment. I was pointing out writecodeonline for some reason is treating y as Y. I don't know why!Ray Toal– Ray Toal2011-09-16 08:14:52 +00:00Commented Sep 16, 2011 at 8:14
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@Ray Toal: Yup, you are right.That's weird.........MD Sayem Ahmed– MD Sayem Ahmed2011-09-16 08:16:07 +00:00Commented Sep 16, 2011 at 8:16
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5 Answers
date("y") == 11 and 11-18 == -7. You need date("Y") == 2011.
Debugging tip: Print out separate parts of the code so you see what's going on. echo $dob shows that the problem is on the first line, and echo date("y")-18 tells that it's the last argument to mktime() that causes it.
Comments
This is the easiest solution :
$dob = strtotime('-18 years');
echo date('d/m/y', $dob);
strtotime() is a powerful function.
Comments
try
$dob = mktime(0, 0, 0, date("m"), date("d")-1, date("Y")-18);
echo "DOB is ".date("d/m/y", $dob);
Comments
According to the manual, when you specify small y as the argument to date function, it will return two-digit representation of the current year. Since the current year is 2011, it will return 11. Subtracting 18 from it will give you a negative result, that's why mktime is resetting to the original timestamp.
Change date("y") to date("Y"), that is, replace small y with capital Y, then you will get the desired result.
Comments
The following code is imho much easier to read:
<?php
$dob = new DateTime();
printf("\nToday is %s", date_format($dob, 'D, M d Y'));
$dob->modify('-1 day');
$dob->modify('-18 year');
printf("\nToday minus %d day and %d year is %s",
-1, -18,
date_format($dob, 'D, M d Y'));
?>
Don't you agree? It is not so difficult to calculate date with PHP. Just look also at the PHP Date function for the various formats, such as Weeknumbers.
