Hey Andrew!
If you are asking what I think you are asking, then I am almost certain that this would be a Handler, yes.
The big issue you have is in determining the customer's time zone (short of straight-out asking them! We have this issue with Dialer. Yes, there are various ways you can use the customer's phone number, but the number is getting to be less and lass reliable as a way of figuring out the physical location (and therefore the time zone). Not only Mobile Phones, but with VoIP services (like Vonage et al) folks are often somewhere other than where their area code would suggest!
Naturally, if the customer is "on file" so to speak, then you may have the information stored in a database and could then simply do a data dip and use the results to determine your offering.
HTH