Hi @michaeljja,
Thank you for your question!
Depending on the ecommerce integration Klaviyo normally updates this based on the IP address or once an order has been placed, on the billing address.
You can however manually import (CSV) the location data (City, State/Region, Country & ZIP code) and this will switch the timezone automatically. If you go down this route I would first export the list into CSV and select those fields, then re-import the data after you changed it in Excel/Google Sheets.
This is especially helpful if the data is incorrect which we sometimes see happen when we migrate from another platform without the eCommerce integration being live first.
More information about this can be found on the help centre here.
Hope that helps!
Thanks
David
Zyber is New Zealand's leading Shopify Premier & Klaviyo Master Platinum Partner passionate about helping merchants succeed. www.zyber.co.nz & www.unlocked.co.nz