I am designing a web page where a user enters a date and time for an action to happen. This action will have a very significant impact on their daily lives, so it is important that the customer understands the time they are entering into the system.
Since these users can be entering this date and time from anywhere in the US, how could I effectively describe the time zone in which they are entering the data? We have no way of knowing where the user is located from customer files with sufficient accuracy. I have considered having a drop down to pick one of the 4 time zones in the continental US, plus Hawaii. Not sure if that is even enough as the user could theoretically be anywhere in the world.