fix(logs): resolve time ranges using client local time zone for logs commands

internal/journal/journal.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"os/exec"
+	"time"
 
 	"github.com/psviderski/uncloud/pkg/api"
 )
@@ -31,11 +32,11 @@ func logs(ctx context.Context, unit string, opts api.ServiceLogsOptions) (io.Rea
 
 	if opts.Since != "" {
 		args = append(args, "-S")
-		args = append(args, opts.Since)
+		args = append(args, journalTimestamp(opts.Since))
 	}
 	if opts.Until != "" {
 		args = append(args, "-U")
-		args = append(args, opts.Until)
+		args = append(args, journalTimestamp(opts.Until))
 	}
 
 	cmd := commandContext(ctx, journalctl, args...)
@@ -51,6 +52,18 @@ func logs(ctx context.Context, unit string, opts api.ServiceLogsOptions) (io.Rea
 	return p, cmd.Wait, nil
 }
 
+// journalTimestamp formats normalised client timestamps for journalctl versions that do not
+// accept RFC 3339 timezone suffixes. Support for timestamps containing T and Z was added in
+// systemd 255 (6 December 2023). Debian 12 ships systemd 252, so it still needs this conversion.
+// Journald timestamps have microsecond precision.
+func journalTimestamp(value string) string {
+	if t, err := time.Parse(time.RFC3339Nano, value); err == nil {
+		return t.UTC().Format("2006-01-02 15:04:05.999999") + " UTC"
+	}
+	// Preserve raw filters from older clients and SDK callers.
+	return value
+}
+
 // follow synchronously follows the io.Reader, writing each new journal entry to channel.
 // It stops when the reader is exhausted or the context is cancelled.
 func follow(ctx context.Context, reader io.Reader, outCh chan api.LogEntry) {

internal/journal/logs_test.go

@@ -115,6 +115,9 @@ func TestEntry(t *testing.T) {
 }
 
 func TestLogs(t *testing.T) {
+	originalCommandContext := commandContext
+	t.Cleanup(func() { commandContext = originalCommandContext })
+
 	commandContext = func(ctx context.Context, _ string, _ ...string) *exec.Cmd {
 		return exec.CommandContext(ctx, "/usr/bin/tail", "testdata/logs")
 	}
@@ -150,3 +153,38 @@ func TestLogs(t *testing.T) {
 	// Still six because heartbeats are not written here and Tail is ignored as the command is overridden.
 	assert.Equal(t, 6, i)
 }
+
+func TestLogs_TimeFilters(t *testing.T) {
+	originalCommandContext := commandContext
+	t.Cleanup(func() { commandContext = originalCommandContext })
+
+	var args []string
+	commandContext = func(ctx context.Context, command string, commandArgs ...string) *exec.Cmd {
+		assert.Equal(t, "journalctl", command)
+		args = commandArgs
+		return exec.CommandContext(ctx, "/usr/bin/tail", "testdata/logs")
+	}
+
+	ch, err := Logs(context.Background(), "uncloud", api.ServiceLogsOptions{
+		Since: "2026-07-01T10:30:45.123456789+10:00",
+		Until: "2026-07-01T01:30:45Z",
+	})
+	require.NoError(t, err)
+	for range ch {
+	}
+	assert.Equal(t, []string{
+		"-u", "uncloud", "--no-hostname", "-n", "0", "-o", "short-unix",
+		"-S", "2026-07-01 00:30:45.123456 UTC",
+		"-U", "2026-07-01 01:30:45 UTC",
+	}, args)
+
+	// Older clients and SDK callers can still pass journalctl's native filters.
+	ch, err = Logs(context.Background(), "uncloud", api.ServiceLogsOptions{Since: "1h ago", Until: "today"})
+	require.NoError(t, err)
+	for range ch {
+	}
+	assert.Equal(t, []string{
+		"-u", "uncloud", "--no-hostname", "-n", "0", "-o", "short-unix",
+		"-S", "1h ago", "-U", "today",
+	}, args)
+}