strtr function in php if translate date but its show 1970

 if you translate date in strtotime and convert into the date its show 1970 01 01 date how to prevent it 

$date = strtr($date_variable, '/', '-');

its translate special/certain character in the string

its important for:

date come in 1970 how to prevent in php

prevent the default time zone 

agar date me convert karne ke baad 1970 ki date aa rahi hai to ye function use kare 

ya fir aap strtotime function use kar sakte hai