Determining where a phone you are calling is located is an important issue for Call Centers as well as other business that want to contact their customers at an appropriate time. You don't want to accidentally call a customer located in Honalulu at 9AM Eastern Time. By better understanding the location and timezone of a phone number, businesses can better target the most appripriate times to reach out to their audience.
Scout makes determining the timezone of any North American number, quick, easy, and inexpensive.
In addition to carrier, porting, and address data, Scout provides the timezone associated with a phone number.
Scout uses the IANA standard for time zones as described here - https://www.iana.org/time-zones
Here are all the U.S. possibilities with corresponding time zones and UTF offsets.