When I use the Stack Exchange data explorer tool (https://data.stackexchange.com/stackoverflow/query/new) for querying data related to the timestamp of the questions, the retrieved value is in which timezone?
Will all the values that are shown be in UTC?
I believe everything is in UTC. Someone asked that same question in the link before on Meta Stack Exchange. It discusses it a bit further but the basic answer to your question is UTC.
https://meta.stackexchange.com/questions/42179/what-time-zone-do-sos-servers-operate-in