fix(cron): honor schedule time zones (#1044)

pkg/cron/service.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"strings"
 	"sync"
 	"time"
 
@@ -286,6 +287,14 @@ func (cs *CronService) computeNextRun(schedule *CronSchedule, nowMS int64) *int6
 
 		// Use gronx to calculate next run time
 		now := time.UnixMilli(nowMS)
+		if tz := strings.TrimSpace(schedule.TZ); tz != "" {
+			loc, err := time.LoadLocation(tz)
+			if err != nil {
+				log.Printf("[cron] failed to load timezone %q: %v", tz, err)
+			} else {
+				now = now.In(loc)
+			}
+		}
 		nextTime, err := gronx.NextTickAfter(schedule.Expr, now, false)
 		if err != nil {
 			log.Printf("[cron] failed to compute next run for expr '%s': %v", schedule.Expr, err)

pkg/cron/service_test.go

@@ -5,6 +5,7 @@ import (
 	"path/filepath"
 	"runtime"
 	"testing"
+	"time"
 )
 
 func TestSaveStore_FilePermissions(t *testing.T) {
@@ -33,6 +34,48 @@ func TestSaveStore_FilePermissions(t *testing.T) {
 	}
 }
 
+func TestComputeNextRun_UsesScheduleTimeZone(t *testing.T) {
+	cs := NewCronService(filepath.Join(t.TempDir(), "cron", "jobs.json"), nil)
+	now := time.Date(2026, time.March, 13, 12, 30, 0, 0, time.UTC).UnixMilli()
+	baseline := cs.computeNextRun(&CronSchedule{Kind: "cron", Expr: "0 9 * * *"}, now)
+	if baseline == nil {
+		t.Fatal("baseline computeNextRun() returned nil")
+	}
+
+	t.Run("uses explicit timezone", func(t *testing.T) {
+		next := cs.computeNextRun(&CronSchedule{
+			Kind: "cron",
+			Expr: "0 9 * * *",
+			TZ:   "America/New_York",
+		}, now)
+		if next == nil {
+			t.Fatal("computeNextRun() returned nil")
+		}
+
+		wantNext := time.Date(2026, time.March, 13, 13, 0, 0, 0, time.UTC).UnixMilli()
+		if *next != wantNext {
+			t.Fatalf("computeNextRun() = %d, want %d", *next, wantNext)
+		}
+		if *next == *baseline {
+			t.Fatal("explicit timezone should change the computed next run for this fixture")
+		}
+	})
+
+	t.Run("falls back to baseline on invalid timezone", func(t *testing.T) {
+		next := cs.computeNextRun(&CronSchedule{
+			Kind: "cron",
+			Expr: "0 9 * * *",
+			TZ:   "Mars/OlympusMons",
+		}, now)
+		if next == nil {
+			t.Fatal("computeNextRun() returned nil")
+		}
+		if *next != *baseline {
+			t.Fatalf("computeNextRun() = %d, want baseline %d", *next, *baseline)
+		}
+	})
+}
+
 func int64Ptr(v int64) *int64 {
 	return &v
 }