The users of the skill we are developing will have either set their address and/or timezone for their device in the Alexa App.
From experimentation with an actual configured Alexa device I can see that when they ask for " Tell me how much Action X ha been done today" Alexa will send to the custom skill the date adjusted for the user local time zone. (I live in Canada and in my experiment I have set the timezone to Russia and then observed Alexa returning tomorrow's date).
My customer has an API from which I need to provide UTC date times to query and get the data to be sent back to users.
My understanding at this time is that my only options available is to try to evaluate and determine the timezone myself in the custom skill by requesting address information from the device.
The ideal solution for this would be that the timezone or offset be included in the all requests sent to my skill (possibly with the device information object).
Another option would be to add to the Amazon to device address api the timezone and offset from the device so my skill could request permission to access and then query for it when needed.