Salesforce: How to Set Up US Timezones with a Custom Formula

salesforce-timezones.txt

# Salesforce Custom Formula for US Timezones based on Billing State
# Note there are 51 because DC counts.
CASE(BillingState, 
"HI","US-PST", 
"AK","US-PST", 
"WA","US-PST", 
"OR","US-PST", 
"CA","US-PST", 
"NV","US-PST", 
"MT","US-MST", 
"WY","US-MST", 
"ID","US-MST", 
"UT","US-MST", 
"CO","US-MST", 
"NM","US-MST", 
"AZ","US-MST", 
"ND","US-CST", 
"MN","US-CST", 
"WI","US-CST", 
"SD","US-CST", 
"IA","US-CST", 
"IL","US-CST", 
"KY","US-CST", 
"TN","US-CST", 
"AL","US-CST", 
"MS","US-CST", 
"AR","US-CST", 
"MO","US-CST", 
"LA","US-CST", 
"TX","US-CST", 
"OK","US-CST", 
"KS","US-CST", 
"NE","US-CST", 
"MI","US-EST", 
"OH","US-EST", 
"IN","US-EST", 
"GA","US-EST", 
"FL","US-EST", 
"SC","US-EST", 
"NC","US-EST", 
"VA","US-EST", 
"WV","US-EST", 
"PA","US-EST", 
"DC","US-EST", 
"MD","US-EST", 
"DE","US-EST", 
"NJ","US-EST", 
"NY","US-EST", 
"VT","US-EST", 
"ME","US-EST", 
"NH","US-EST", 
"RI","US-EST", 
"CT","US-EST", 
"MA","US-EST", 
"-")

What about states that have multiple time zones? Florida for example is in both Eastern and Central time.