time: restore support for large negative days in Date
CL 586257 converted days to uint32 which is usually fine but fails for
negative days close to cycle boundaries.
Fixes #68718
Change-Id: I8dc5b8fe0c7c1921beb204da1913b9a1ab39280d
Reviewed-on: https://go-review.googlesource.com/c/go/+/602815 Reviewed-by: Rob Pike <r@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com> Reviewed-by: Michael Knyszek <mknyszek@google.com> Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>