Which your version of the stack?
If you go to advanced settings - you can set the timezone - default is browser.
If you want to change the timefield to a different date on the UI - its being worked on right now ability to set human readable title of data view & ability to edit data view by shivindera · Pull Request #124191 · elastic/kibana · GitHub
If you want to change it at source then you will have to modify your index. There is an example here - Changing the default timestamp after creating index pattern
Thanks,
Bhavya