Timezone data source freshness lag relative to IANA tzdata updates

Answer to the Core Questions

• Typical delay: 1–2 months. Terraform 1.5 uses the Go runtime bundled with its release; Go updates its embedded zoneinfo.zip only on new Go releases, which follow a roughly monthly cadence.
• Validation without external APIs: Run a minimal Go program that loads the target IANA zone via time.LoadLocation("Region/City"), prints the current UTC offset, abbreviation, and DST status, then compare those values against the latest tzdata snapshot. This can be automated in CI with terraform local‑exec or a standalone test step.
• Metadata exposure: The Terraform timezone data source does not expose a field that reveals the tzdata version it was compiled against. You must infer it from the Go runtime version used by the Terraform binary or by inspecting the Go source tree that built the binary.

Practical Validation Steps

1. Identify the Go version shipped with your Terraform binary:

   terraform version
   # Look for the "Go" line, e.g., "Go 1.22.1"
   

2. Locate the bundled zoneinfo.zip:

   go env GOROOT
   # zoneinfo.zip is typically at $GOROOT/lib/time/zoneinfo.zip
   

3. Create a Go test file (e.g., tzcheck.go):

   package main
   
   import (
       "fmt"
       "time"
   )
   
   func main() {
       loc, err := time.LoadLocation("Europe/Paris")
       if err != nil {
           panic(err)
       }
       now := time.Now().In(loc)
       fmt.Printf("Offset: %d, Abbrev: %s, DST: %t\n", now.UTC().Sub(now).Hours()*3600, now.Format("Z"), now.IsDST())
   }
   

4. Run the program:

   go run tzcheck.go
   

5. Compare the printed values with the corresponding rules in the latest tzdata snapshot (downloaded from https://www.iana.org/time-zones). If they match, the embedded database is up‑to‑date for that region.

When to Ask for More Information

The recommendation above assumes you are using a stable Terraform release that follows the standard Go release cycle. If you are on a custom or pre‑release build, or if you need to verify support for a very recent IANA change, please provide the exact Terraform version and the Go runtime version it was compiled with. That detail will help narrow the expected lag window.