výpočet 18 let zpět datum v php
date('Y-m-d', strtotime('18 years ago'))
jak se dostat n dní ode dneška v php
//Simple method how to get the date of tomorrow, yesterday, etc. is to use:
$tomorrow = date( "Ymd", strtotime( "+1 days" ) );
$dayaftertomorrow = date( "Ymd", strtotime( "+2 days" ) );
$yesterday = date( "Ymd", strtotime( "-1 days" ) );