This is the article of an example of how to fix timezone issue with playSMS.

This is my server’s time, its in UTC:

$ date
Wed Aug 1 03:22:21 UTC 2018

And then I check where is my php.ini, both for php-cli and php-fpm (I’m using Nginx with php-fpm):

$ php -i | grep php.ini
Configuration File (php.ini) Path => /etc/php/7.0/cli
Loaded Configuration File => /etc/php/7.0/cli/php.ini

I looked for date.timezone option on php.ini, edit it and set the option to my timezone Asia/Jakarta, its UTC+7. When done it will be like this:

$ cat /etc/php/7.0/cli/php.ini | grep date.timezone
; http://php.net/date.timezone
date.timezone = Asia/Jakarta

I also set it in php-fpm php.ini, not just php-cli php.ini:

$ cat /etc/php/7.0/fpm/php.ini | grep date.timezone
; http://php.net/date.timezone
date.timezone = Asia/Jakarta

Please note you need to restart php-fpm when you changed php-fpm php.ini.

In playSMS I set my default timezone to +0700 (its UTC+7):

Restart playsmsd and do some test, for example send an SMS with a schedule.

As a reference please read this:
https://playsms.org/2013/12/07/fix-timezone-problem/