Add daily timezone drift check

tz-drift-check.sh + sky-cam-tzcheck timer notify when TIMEZONE no longer
matches the machine's timezone (timers follow the machine, scripts follow TIMEZONE).

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013wi3ZRpfenCe2TRwT4JFMG

daily_sunrise_video.sh

@@ -65,14 +65,16 @@ if ! $TEST_MODE; then
     start_sec=$((sunrise_sec - SUNRISE_PRE_MIN * 60))
     end_sec=$((sunrise_sec + SUNRISE_POST_MIN * 60))
     echo "Window: $((start_sec/3600)):$(printf '%02d' $(((start_sec%3600)/60))) → $((end_sec/3600)):$(printf '%02d' $(((end_sec%3600)/60)))"
-    midnight=$(date -d "today 00:00:00" +%s)
-    now_day_sec=$(( $(date +%s) - midnight ))
-    if [ "$now_day_sec" -lt "$end_sec" ]; then
-        wait_sec=$(( end_sec - now_day_sec + 30 ))
-        echo "Waiting ${wait_sec}s for capture window to finish (ends $(date -d "@$(( midnight + end_sec ))" '+%H:%M:%S'))..."
+    # Resolve wall-clock targets through `date -d` instead of adding seconds-since-
+    # midnight to a midnight epoch: on a DST day (23h/25h) the two differ by 3600s.
+    end_epoch=$(date -d "today $(printf '%02d:%02d:%02d' $((end_sec/3600)) $(((end_sec%3600)/60)) $((end_sec%60)))" +%s)
+    now_epoch=$(date +%s)
+    if [ "$now_epoch" -lt "$end_epoch" ]; then
+        wait_sec=$(( end_epoch - now_epoch + 30 ))
+        echo "Waiting ${wait_sec}s for capture window to finish (ends $(date -d "@$end_epoch" '+%H:%M:%S'))..."
         sleep "$wait_sec"
     else
-        echo "Capture window already closed at $(date -d "@$(( midnight + end_sec ))" '+%H:%M:%S') — processing available images"
+        echo "Capture window already closed at $(date -d "@$end_epoch" '+%H:%M:%S') — processing available images"
     fi
 fi
 

install.sh

@@ -296,6 +296,25 @@ for cam in "${CAMERAS[@]}"; do
     fi
 done
 
+# ── Timezone drift check ─────────────────────────────────────────────────────
+# Daily + shortly after boot: notify if TIMEZONE no longer matches the
+# machine's timezone (systemd timers follow the machine, scripts follow TIMEZONE).
+write_service "sky-cam-tzcheck" "timezone drift check" "tz-drift-check.sh"
+cat > "$UNIT_DIR/sky-cam-tzcheck.timer" <<EOF2
+[Unit]
+Description=Sky-Cam — timezone drift check
+
+[Timer]
+OnBootSec=3min
+OnCalendar=*-*-* 12:00:00
+Persistent=true
+
+[Install]
+WantedBy=timers.target
+EOF2
+echo "  wrote sky-cam-tzcheck.timer"
+timers+=("sky-cam-tzcheck")
+
 # ── Generate .env.example ────────────────────────────────────────────────────
 env_example="$HERE/.env.example"
 {

sunrise-audio-capture.sh

@@ -54,12 +54,13 @@ record_dur_sec=$SUNRISE_TARGET_SECS
 
 echo "Audio window: ${half_pre}s before → ${half_post}s after sunrise (${record_dur_sec}s total)"
 
-midnight=$(date -d "today 00:00:00" +%s)
-now_day_sec=$(( $(date +%s) - midnight ))
-wait_sec=$(( record_start_sec - now_day_sec ))
+# Resolve the wall-clock start via `date -d` (not midnight epoch + seconds):
+# on a DST day (23h/25h) those differ by 3600s.
+start_epoch=$(date -d "today $(printf '%02d:%02d:%02d' $((record_start_sec/3600)) $(((record_start_sec%3600)/60)) $((record_start_sec%60)))" +%s)
+wait_sec=$(( start_epoch - $(date +%s) ))
 
 if [ "$wait_sec" -gt 0 ]; then
-    echo "Waiting ${wait_sec}s until audio window ($(date -d "@$(( midnight + record_start_sec ))" '+%H:%M:%S'))..."
+    echo "Waiting ${wait_sec}s until audio window ($(date -d "@$start_epoch" '+%H:%M:%S'))..."
     sleep "$wait_sec"
 fi
 

sunrise.py

@@ -58,7 +58,9 @@ tz        = pytz.timezone(conf['TIMEZONE'])
 # This bracket is timezone-correct and handles any UTC offset, including large
 # positive offsets (UTC+12/+14) where local midnight falls on the previous UTC day.
 now_local     = datetime.now(tz)
-midnight_local = now_local.replace(hour=0, minute=0, second=0, microsecond=0)
+# tz.localize (not .replace) so the UTC offset is re-resolved for midnight —
+# on a DST-change day now_local's offset differs from midnight's.
+midnight_local = tz.localize(datetime(now_local.year, now_local.month, now_local.day))
 t0_utc = midnight_local.astimezone(timezone.utc)
 t1_utc = t0_utc + timedelta(hours=25)   # 25 h covers any timezone's full day
 

tz-drift-check.sh

@@ -0,0 +1,49 @@
+#!/bin/bash
+# tz-drift-check.sh — warn if TIMEZONE (sky-cam.conf / .env) no longer matches
+# the machine's own timezone.
+#
+# systemd timers fire on the machine's clock, but sunrise.py, the capture
+# scripts and the per-day folder names use TIMEZONE. If the two drift apart
+# (someone ran `timedatectl set-timezone`, a cloud-init reset, a restored
+# image, a typo in .env...) every scheduled job runs at the wrong local time
+# and the sunrise capture window is off by the zone difference.
+#
+# Run daily by sky-cam-tzcheck.timer (and shortly after boot). Sends one
+# notify.sh message per run while the mismatch persists; silent when fine.
+# Exit 0 either way — a mismatch is a notification, not a job failure.
+
+set -uo pipefail
+
+SCRIPT_DIR="$(dirname "$(realpath "$0")")"
+source "$SCRIPT_DIR/sky-cam.conf"
+source "$SCRIPT_DIR/.env" 2>/dev/null || true
+
+# Machine's zone — read WITHOUT any TZ override so we see the real system value.
+sys_tz="$(env -u TZ timedatectl show -p Timezone --value 2>/dev/null)"
+[ -z "$sys_tz" ] && sys_tz="$(cat /etc/timezone 2>/dev/null)"
+[ -z "$sys_tz" ] && sys_tz="$(readlink /etc/localtime 2>/dev/null | sed 's|.*/zoneinfo/||')"
+if [ -z "$sys_tz" ]; then
+    echo "tz-drift-check: could not determine the machine's timezone — skipping"
+    exit 0
+fi
+
+# Compare by real UTC offsets across the year so aliases (US/Eastern vs
+# America/New_York) and identical-rule zones are not reported as drift.
+same=true
+if [ "$sys_tz" != "$TIMEZONE" ]; then
+    for m in 01 04 07 10; do
+        a="$(TZ="$sys_tz"   date -d "2026-$m-15 12:00 UTC" +%z)"
+        b="$(TZ="$TIMEZONE" date -d "2026-$m-15 12:00 UTC" +%z)"
+        [ "$a" = "$b" ] || { same=false; break; }
+    done
+fi
+
+if $same; then
+    echo "Timezone OK: sky-cam TIMEZONE=$TIMEZONE, machine=$sys_tz"
+    exit 0
+fi
+
+msg="sky-cam TIMEZONE is $TIMEZONE but this machine's timezone is $sys_tz. Scheduled jobs run on the machine clock, so sunrise/seasons/moon jobs will fire at the wrong local time. Fix: set TIMEZONE=$sys_tz in $SCRIPT_DIR/.env and re-run ./install.sh, or run: sudo timedatectl set-timezone $TIMEZONE"
+echo "WARNING: $msg"
+"$SCRIPT_DIR/notify.sh" "WARNING: sky-cam timezone mismatch" "$msg" || true
+exit 0