more idiomatic makefile

Reviewed-on: #6

Makefile

@@ -3,7 +3,7 @@
 
 # Target bodies live in script/ (Scripts to Rule Them All); the targets
 # below are thin shims that call them.
-.DEFAULT_GOAL := check
+.DEFAULT_GOAL := build
 
 VERSION ?= $(shell git describe --tags --always)
 
@@ -37,7 +37,9 @@ cibuild:
 hooks:
 	@script/install-precommit
 
-build:
+build: ./bin/rtnetmon
+
+./bin/rtnetmon: ./cmd ./internal go.sum go.mod
 	CGO_ENABLED=0 go build -trimpath -ldflags "-X main.Version=$(VERSION)" \
 		-o bin/rtnetmon ./cmd/rtnetmon
 

internal/monitor/export_test.go

@@ -2,6 +2,7 @@ package monitor
 
 import (
 	"context"
+	"time"
 
 	"git.eeqj.de/sneak/rtnetmon/internal/starlink"
 )
@@ -59,6 +60,9 @@ func (m *Monitor) TCPHosts() []string { return m.tcpHosts }
 // Interfaces returns the monitored interfaces.
 func (m *Monitor) Interfaces() []*InterfaceStatus { return m.interfaces }
 
+// ClockStrings exposes clockStrings for external tests.
+func ClockStrings(now time.Time) (string, string) { return clockStrings(now) }
+
 // PingArgs exposes pingArgs for external tests.
 func PingArgs(goos, iface, host string) []string { return pingArgs(goos, iface, host) }
 

internal/monitor/ui.go

@@ -337,6 +337,15 @@ func drawICMPStats(scr tcell.Screen, y int, st *InterfaceStatus) int {
 }
 
 // uiLoop runs the UI event loop.
+// clockFormat is the layout of both header clocks.
+const clockFormat = time.RFC1123Z
+
+// clockStrings renders the header clocks: UTC first, then the host's local
+// time in whatever location now carries.
+func clockStrings(now time.Time) (string, string) {
+	return now.UTC().Format(clockFormat), now.Format(clockFormat)
+}
+
 func (m *Monitor) uiLoop(ctx context.Context) {
 	m.logf("UI loop started")
 
@@ -348,13 +357,6 @@ func (m *Monitor) uiLoop(ctx context.Context) {
 		m.logf("Screen finalized")
 	}()
 
-	pstLoc, err := time.LoadLocation("America/Los_Angeles")
-	if err != nil {
-		m.logf("Error loading PST location: %v", err)
-
-		pstLoc = time.UTC
-	}
-
 	timestampSpinFrame := 0
 	lastTimestampSpinUpdate := time.Now()
 
@@ -365,8 +367,7 @@ func (m *Monitor) uiLoop(ctx context.Context) {
 		Put(m.screen, colLeft, rowTopRule, HLine(w), tcell.StyleDefault)
 
 		now := time.Now()
-		timeStr := now.Format(time.RFC1123Z)
+		timeStr, localTimeStr := clockStrings(now)
-		pstTimeStr := now.In(pstLoc).Format(time.RFC1123Z)
 
 		if time.Since(lastTimestampSpinUpdate) >= time.Second {
 			timestampSpinFrame = (timestampSpinFrame + 1) % len(brailleSpins())
@@ -380,7 +381,7 @@ func (m *Monitor) uiLoop(ctx context.Context) {
 		Put(m.screen, colSpinner, rowClock, string(brailleChar)+" ", tcell.StyleDefault)
 		DrawRainbowText(m.screen, colMeter, rowClock, timeStr, colors)
 		DrawRainbowText(m.screen, colMeter+len(timeStr)+clockGap, rowClock,
-			pstTimeStr, colors)
+			localTimeStr, colors)
 		Put(m.screen, colLeft, rowBottomRule, HLine(w), tcell.StyleDefault)
 
 		runtime := time.Since(m.startTime).Round(time.Second).String()

internal/monitor/ui_test.go

@@ -0,0 +1,27 @@
+package monitor_test
+
+import (
+	"testing"
+	"time"
+
+	"git.eeqj.de/sneak/rtnetmon/internal/monitor"
+)
+
+// TestClockStrings checks that the header shows UTC first and the host's
+// local time second, so the two differ whenever the host is not on UTC.
+func TestClockStrings(t *testing.T) {
+	t.Parallel()
+
+	berlin := time.FixedZone("CET", 3600)
+	now := time.Date(2026, time.November, 6, 20, 30, 0, 0, berlin)
+
+	utc, local := monitor.ClockStrings(now)
+
+	if want := "Fri, 06 Nov 2026 19:30:00 +0000"; utc != want {
+		t.Errorf("utc = %q, want %q", utc, want)
+	}
+
+	if want := "Fri, 06 Nov 2026 20:30:00 +0100"; local != want {
+		t.Errorf("local = %q, want %q", local, want)
+	}
+}