fix: evaluate schedules in the cronjob's spec.timeZone

Schedules were always evaluated in UTC, so a cronjob with timeZone set (e.g. 0 7 * * * Europe/Stockholm) was reported as not running every day. Embed tzdata since the image is built from scratch.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01C8SW6vsbkrTKjLNatQ8JTg

main.go

@@ -8,6 +8,7 @@ import (
 	"os/signal"
 	"syscall"
 	"time"
+	_ "time/tzdata" // the image is FROM scratch, so embed zoneinfo for spec.timeZone
 
 	"github.com/alecthomas/kingpin/v2"
 	"github.com/multiplay/go-slack/chat"
@@ -19,8 +20,10 @@ import (
 	"k8s.io/client-go/rest"
 )
 
-var checkFunc = doCheck
-var exitFunc = os.Exit
+var (
+	checkFunc = doCheck
+	exitFunc  = os.Exit
+)
 
 func main() {
 	slackUrl := kingpin.Flag("slack-url", "The Slack Webhook URL").Envar("SLACK_URL").Required().String()
@@ -68,6 +71,14 @@ func doCheck(client Client, slackUrl string, ic chan os.Signal, sleepTime time.D
 					if c.Status.LastScheduleTime != nil {
 						since = *c.Status.LastScheduleTime
 					}
+					// The schedule is evaluated in the location of since, so use the cronjob's time zone (UTC if unset)
+					if c.Spec.TimeZone != nil {
+						loc, err := time.LoadLocation(*c.Spec.TimeZone)
+						if err != nil {
+							return fmt.Errorf("error loading time zone of %s/%s (%s): %w", c.Namespace, c.Name, *c.Spec.TimeZone, err)
+						}
+						since = v1.NewTime(since.In(loc))
+					}
 					schedule, err := parser.Parse(c.Spec.Schedule)
 					if err != nil {
 						return fmt.Errorf("error parsing schedule of %s/%s (%s): %w", c.Namespace, c.Name, c.Spec.Schedule, err)