Linux machines use UTC clock so does bash script, If your script needs time from a different timezone then you have to convert current UTC to let's say PDT, how do we do it in bash. 
    
Python has widely used programing language and has lots of libraries for this, But funny this is bash very answer for this, just export TZ variable. As simple as this. 

Let's try this snippet on a Linux machine. It prints time from 3 timezones PDT, UTC, and IST.

gil@localhost:/home/gil# TZ=America/Los_Angeles date ;date ; TZ=Asia/Kolkata date
Wed Jul 22 13:42:56 PDT 2020
Wed Jul 22 20:42:56 UTC 2020
Thu Jul 23 02:12:56 IST 2020
view raw timezone.txt hosted with ❤ by GitHub
If you notice I'm not exporting  TZ, just using variable while running date command, You can simply do export TZ=America/Los_Angeles, but if you export then you can't use UTC unless you change it back to UTC.