diff --git a/README.md b/README.md
index 38afa82..de517d7 100644
--- a/README.md
+++ b/README.md
@@ -16,7 +16,7 @@
 
 ⚡️ Delivers core agent functionality in just **~4,000** lines of code — **99% smaller** than Clawdbot's 430k+ lines.
 
-📏 Real-time line count: **3,668 lines** (run `bash core_agent_lines.sh` to verify anytime)
+📏 Real-time line count: **3,689 lines** (run `bash core_agent_lines.sh` to verify anytime)
 
 ## 📢 News
 
diff --git a/nanobot/agent/tools/cron.py b/nanobot/agent/tools/cron.py
index 9dc31c2..b10e34b 100644
--- a/nanobot/agent/tools/cron.py
+++ b/nanobot/agent/tools/cron.py
@@ -99,6 +99,12 @@ class CronTool(Tool):
             return "Error: no session context (channel/chat_id)"
         if tz and not cron_expr:
             return "Error: tz can only be used with cron_expr"
+        if tz:
+            from zoneinfo import ZoneInfo
+            try:
+                ZoneInfo(tz)
+            except (KeyError, Exception):
+                return f"Error: unknown timezone '{tz}'"
         
         # Build schedule
         delete_after = False
diff --git a/nanobot/cli/commands.py b/nanobot/cli/commands.py
index 3b58db5..3798813 100644
--- a/nanobot/cli/commands.py
+++ b/nanobot/cli/commands.py
@@ -719,17 +719,15 @@ def cron_list(
     table.add_column("Status")
     table.add_column("Next Run")
     
-    import datetime
     import time
+    from datetime import datetime as _dt
     from zoneinfo import ZoneInfo
     for job in jobs:
         # Format schedule
         if job.schedule.kind == "every":
             sched = f"every {(job.schedule.every_ms or 0) // 1000}s"
         elif job.schedule.kind == "cron":
-            sched = job.schedule.expr or ""
-            if job.schedule.tz:
-                sched = f"{sched} ({job.schedule.tz})"
+            sched = f"{job.schedule.expr or ''} ({job.schedule.tz})" if job.schedule.tz else (job.schedule.expr or "")
         else:
             sched = "one-time"
         
@@ -737,13 +735,10 @@ def cron_list(
         next_run = ""
         if job.state.next_run_at_ms:
             ts = job.state.next_run_at_ms / 1000
-            if job.schedule.kind == "cron" and job.schedule.tz:
-                try:
-                    dt = datetime.fromtimestamp(ts, ZoneInfo(job.schedule.tz))
-                    next_run = dt.strftime("%Y-%m-%d %H:%M")
-                except Exception:
-                    next_run = time.strftime("%Y-%m-%d %H:%M", time.localtime(ts))
-            else:
+            try:
+                tz = ZoneInfo(job.schedule.tz) if job.schedule.tz else None
+                next_run = _dt.fromtimestamp(ts, tz).strftime("%Y-%m-%d %H:%M")
+            except Exception:
                 next_run = time.strftime("%Y-%m-%d %H:%M", time.localtime(ts))
         
         status = "[green]enabled[/green]" if job.enabled else "[dim]disabled[/dim]"
diff --git a/nanobot/cron/service.py b/nanobot/cron/service.py
index 9fda214..14666e8 100644
--- a/nanobot/cron/service.py
+++ b/nanobot/cron/service.py
@@ -32,7 +32,7 @@ def _compute_next_run(schedule: CronSchedule, now_ms: int) -> int | None:
         try:
             from croniter import croniter
             from zoneinfo import ZoneInfo
-            # Use the caller-provided reference time for deterministic scheduling.
+            # Use caller-provided reference time for deterministic scheduling
             base_time = now_ms / 1000
             tz = ZoneInfo(schedule.tz) if schedule.tz else datetime.now().astimezone().tzinfo
             base_dt = datetime.fromtimestamp(base_time, tz=tz)
diff --git a/nanobot/skills/cron/SKILL.md b/nanobot/skills/cron/SKILL.md
index 7db25d8..cc3516e 100644
--- a/nanobot/skills/cron/SKILL.md
+++ b/nanobot/skills/cron/SKILL.md
@@ -30,6 +30,11 @@ One-time scheduled task (compute ISO datetime from current time):
 cron(action="add", message="Remind me about the meeting", at="<ISO datetime>")
 ```
 
+Timezone-aware cron:
+```
+cron(action="add", message="Morning standup", cron_expr="0 9 * * 1-5", tz="America/Vancouver")
+```
+
 List/remove:
 ```
 cron(action="list")
@@ -44,4 +49,9 @@ cron(action="remove", job_id="abc123")
 | every hour | every_seconds: 3600 |
 | every day at 8am | cron_expr: "0 8 * * *" |
 | weekdays at 5pm | cron_expr: "0 17 * * 1-5" |
+| 9am Vancouver time daily | cron_expr: "0 9 * * *", tz: "America/Vancouver" |
 | at a specific time | at: ISO datetime string (compute from current time) |
+
+## Timezone
+
+Use `tz` with `cron_expr` to schedule in a specific IANA timezone. Without `tz`, the server's local timezone is used.