@Vivek Komarla Bhaskar Thanks for reaching out. Your function expression looks good and as per the error message looks like the value for destination inside the convertTimeZone is not correct string. I will suggest you edit the expression again and manually type it again and confirm if you still observe the same issue. There is a chance that when you copy paste the content then there may be special characters that are added to the actual content, and it would not be visible as the simple text. That is the reason you are not able to see when you may have reviewed the expression and in the error message. I was able to reproduce the issue with the same error if I add special character to my content GMT Standard Time.
Let me know if you need any assistance.