time: check for time zone offset overflow

time: check for time zone offset overflow

Fixes #67470

Change-Id: Idc5997859602ff6155aa9ae875b327fbcb53513d
Reviewed-on: https://go-review.googlesource.com/c/go/+/586717
Reviewed-by: Alan Donovan <adonovan@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Commit-Queue: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>