I want to add 100 years to the displayed wordpress dates - php

Question

I'm going to create a "future"-blogg (sort of a sci-fi-adventure in blog form) and want to display all dates +100 years. For instance a post published 2012-05-17 should display the date 2112-05-17.
First I thought I could just easily set the date to 2112-05-17, but it seems that wordpress can't handle dates higher than 2049.
So my next idea is to modify how the dates are displayed. I was thinking of modifying get_the_date() in general-template.php, and make it return the later date.
But here my skills are not enough. I don't know anything about how to work with date values in php.
get_the_date() looks like this:
function get_the_date( $d = '' ) {
global $post;
$the_date = '';
if ( '' == $d )
$the_date .= mysql2date(get_option('date_format'), $post->post_date);
else
$the_date .= mysql2date($d, $post->post_date);
return apply_filters('get_the_date', $the_date, $d);
}
Any ideas on how to modify it? So it adds 100 years to the date before returning it?
Any input would be appriciated :)

Answer 1

Looks like you might need to investigate date_modify and also strtotime
http://php.net/manual/en/datetime.modify.php
http://www.php.net/manual/en/function.strtotime.php
http://www.php.net/manual/en/datetime.add.php

Answer 2

Assuming your mysql dates are of the following format: YYYY-MM-DD
function add100yr( $date="2011-03-04" ) {
$timezone=date_timezone_get();
date_default_timezone_set($timezone);
list($year, $month, $day) = split(':', $date);
$timestamp=mktime(0,0,0, $month, $day, $year);
// 100 years, 365.25 days/yr, 24h/day, 60min/h, 60sec/min
$seconds = 100 * 365.25 * 24 * 60 * 60;
$newdate = date("Y-m-d", $timestamp+$seconds );
// $newdate is now formatted YYYY-mm-dd
}
Now you can:
function get_the_date( $d = '' ) {
global $post;
$the_date = '';
if ( '' == $d )
$the_date .= mysql2date(get_option('date_format'), add100yr($post->post_date));
else
$the_date .= mysql2date($d, add100yr($post->post_date));
return apply_filters('get_the_date', $the_date, $d);
}

Answer 3

Try a custom field: http://codex.wordpress.org/Custom_Fields
You will have to enter the +100 year date for each post, but then you're not going to be relying on php or functions to alter the current date.

Answer 4

WordPress provides the filter get_the_date that allows to modify the value before it is handled over to the theme or plugin.
This filter is used everytime get_the_date() is called.
add_filter( 'get_the_date', 'modify_get_the_date', 10, 3 );
function modify_get_the_date( $value, $format, $post ) {
$date = new DateTime( $post->post_date );
$date->modify( "+100 years" );
if ( $format == "" )
$format = get_option( "date_format" );
return( $date->format( $format ) );
}
This function takes the post_date from the post, adds the time and returns it according to the format given to get_the_date() or with the default format configured in the WordPress options.