Using SQL Server datetimeoffset

Question

I am trying to store the date, time and timezone of a meeting that is set up within a tool. I allow the user to specify the date and time as well as select from a timezone list.

My issue is trying to figure out how to take all 3 parts and format it into a correct datetimeoffset to store.

I believe this is the format that SQL Server needs for datetimeoffset:

YYYY-MM-DD hh:mm:ss[.nnnnnnn] [{+|-}hh:mm]

My first question with this is what should the values of my timezone drop down be?

Secondly, is there a built in way in SQL Server to pass this string of data and convert it into the format needed for datetimeoffset?