We'll create fresh WordPress site with Timezone Conversion Widget installed. You have 20 minutes to test the plugin after that site we'll be deleted.
This is a light weight plugin which allows your customer to convert the time from one timezone to another timezone.
Basically, this plugin add a Timezone Conversion widget, which shows the date & time, from timezone and to timezone selection field on the front end of website.
Visitor can select date and time, from and to timezone from the dropdown and submission of it will show the converted date & time.