I need to send sms globally to different timezones  to each customer registered online
The messages are scheduled to be send each month.
I have the country details of each cutomer . I would be writing a python script and add it to cronjobs for sending sms.
The issue I am facing is knowing a safe time ( sometime during the day)  based on the country for sending the SMS.
MY server runs in Australian/Melbourne timezone.What is the best way for me to find the safe time to send SMS to a customer from another country
You probably want to store each user's timezone in your database and then you can change a particular datetime object's timezone by using datetime.astimezone(tz) . 
Now deciding what a good time to to sms them is entirely up to you.
Dealing with timezones for sending sms -python /django