How should I store dates in RavenDB? Using UTC? Using Local Time?
When you store a date to RavenDB, it will save whether it's UTC or not. When it's not UTC, a local date is treated as "Unspecified".
However if you have people from around the world using the same database, and you use unspecified local times, the offset is not stored. If you want to deal with this scenario you need to store the date using a DateTimeOffset that will store the date and time, and its time zone offset.
The decision of whether to use UTC, or Local Time, or DateTimeOffset is an application decision, not an infrastructure decision. There are valid reasons for using any one of these.