>>>Who knew? Well, Google did -- first entry, first search: https://greatdata.com/pdf/ac-tz.pdf (entries with an * have 2 time zones).
>>>
>>My question is what should we do with the cases when area code crosses two time zones.
>
>There is actually a way to pinpoint areas within an area code. There is the area code (first 3 numbers), then there is the prefix (next 3 numbers), and then the last four numbers. The 3 numbers that make the prefix are areas within the area code. For example, 310 is an area code that covers West Los Angeles and South Bay areas of Los Angeles County, including Santa Catalina Island. and a small portion of Ventura County. If the prefix is 589 then that narrows it down to just Malibu. In addition you can also tell by the prefix if it's a landline (which 589 happens to be) or wireless. ..so if a phone number is 310-589-xxxx then you know it's a landline in Malibu. Now assuming that one city doesn't sit it two time zones (and I don't think there is any such city in the USA) that should work.
>
>
>
>>>>Hi,
>>>>
>>>>I am wondering how many states in US have different time zones in the state itself and if there are different time zones per area code?
>>>>
>>>>If this is the case, how can we figure out the GMT date /time based on the area code and the time which most likely was recorded in local time?
>>>>
>>>>Thanks in advance.

I do vaguely recall a few occasions where there were businesses in Los Angeles with phone numbers that would indicate that they were situated in a more affluent neighborhood, but their normal mailing address would suggest otherwise -- I don't recall if this was because these phones numbers were for mobile rather than landline.
I also recall back when my parents and several of our neighbors were sharing a multi-party telephone line. When it was decided to eventually switch to individual telephone lines, one neighbor ended up with a phone number that would suggest they lived in a different city. My parents and one other neighbor opted to keep the original phone number rather than change.