Converting a date differnce into a timestamp in seconds from a date that is before 1970 relative to now. PHP

Question

I need to find a way to find out how to produce a timestamp in seconds that represents the interval between a date that is before 1970 to the current time.

X persons birthday 1969-01-02

Current Day 2013-08-23

I tried

<?php
$then = new DateTime("1969-01-02");
$age = $then->getTimestamp();
?>

Gave me a minus timestamp up until 1970.

I have also done a date difference

<?php
    $then = new DateTime("1969-01-02");
    $now = new DateTime("now");
    $age = $then->diff($now);
?>

But I don't know how to convert the date difference into a seconds timestamp that I can use. Any help please?

The reason I ask is that when performing a timestamp on a date after 1970 relative to now it works fine and gives the expected output. But if someones birthday is before 1970 it will just calculat the timestamp of their date of birth until 1970 which is totally inaccurate. So I need to find a way to get a timestamp of their age in seconds for people with date of births before 1970.

What is wrong with a negative time stamp? It calculates just as well as positive ones. — Carsten Massmann
To get age, try this: stackoverflow.com/questions/3776682/php-calculate-age or this stackoverflow.com/questions/3380990/… - is it really so hard to find? — Alma Do

Rohan Kumar Rohan Kumar · Accepted Answer · 2013-08-23T11:03:46

That's the expected behavior.

UNIX timestamp is the number of seconds since Jan 1 1970 (not considering leap seconds). For dates before that, it will return a negative number.

Yes, if you want to calculate the years, months and days then try this,

<?php
    $then = new DateTime("1969-01-02");
    $now = new DateTime('now');
    $age = $then->diff($now);
    echo $age->format('%Y years, %m months,%d days');
?>

Updated,

<?php
    $then = strtotime("1969-01-02");
    $now = strtotime('now');

    $age=$now-$then;
    // Above is your final time stamp, created by the difference of two dates

    $diff = abs($age);
    $years = floor($diff / (365*60*60*24));
    $months = floor(($diff - $years * 365*60*60*24) / (30*60*60*24));
    $days = floor(($diff - $years * 365*60*60*24 - $months*30*60*60*24)/ (60*60*24));
    printf("%d years, %d months, %d days\n", $years, $months, $days);
    // Outputs-> 44 years, 8 months, 4 days 
?>

Converting a date differnce into a timestamp in seconds from a date that is before 1970 relative to now. PHP

1 Answers