Support setting a timezone with `process.env.TZ` and `Bun.env.TZ` (#3018)

* Support setting a timezone via `process.env.TZ`

* Implement `setTimeZone` in `bun:jsc` module

* [breaking] `bun:test` now defaults to `Etc/UTC` timezone

---------

Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/bun_js.zig b/src/bun_js.zig
index 5a4eb4f8a..00cb51d20 100644
--- a/src/bun_js.zig
+++ b/src/bun_js.zig
@@ -204,6 +204,13 @@ pub const Run = struct {
         vm.is_main_thread = true;
         JSC.VirtualMachine.is_main_thread_vm = true;
 
+        // Allow setting a custom timezone
+        if (vm.bundler.env.get("TZ")) |tz| {
+            if (tz.len > 0) {
+                _ = vm.global.setTimeZone(&JSC.ZigString.init(tz));
+            }
+        }
+
         var callback = OpaqueWrap(Run, Run.start);
         vm.global.vm().holdAPILock(&run, callback);
     }