diff --git a/src/shared/python/shared/blocks.py b/src/shared/python/shared/blocks.py
index 704fa1c..7d35abe 100644
--- a/src/shared/python/shared/blocks.py
+++ b/src/shared/python/shared/blocks.py
@@ -8,6 +8,12 @@ EASTERN = ZoneInfo("America/New_York")
 WEEKEND_DAYS = {"Saturday", "Sunday"}
 
 
+SHIFT_LABELS = {
+    "day": "Day (8am–5pm)",
+    "night": "Night (5pm–8am)",
+}
+
+
 def _format_shift_line(
     date: datetime,
     ext: str,
@@ -17,8 +23,8 @@ def _format_shift_line(
     shift_type: str = "night",
 ) -> str:
     day_label = date.strftime("%a %b %-d")
-    if shift_type == "day":
-        day_label += " (Day 8a–5p)"
+    if shift_type in SHIFT_LABELS:
+        day_label += f" {SHIFT_LABELS[shift_type]}"
     if is_today:
         day_label = f"*{day_label} (today)*"
 
@@ -56,17 +62,19 @@ def build_week_schedule(schedule, start_date: datetime | None = None) -> list[di
         day_name = date.strftime("%A")
         is_today = date_str == today_str
 
+        is_past = date_str < today_str
+
         # Weekend day shift (8am–5pm)
         if day_name in WEEKEND_DAYS:
             ext, name, source = schedule.resolve_shift(date_str, day_name, "day")
             lines.append(_format_shift_line(date, ext, name, source, is_today, "day"))
-            if source == "available":
+            if source == "available" and not is_past:
                 open_shifts.append((date_str, "day"))
 
         # After-hours (night) shift
         ext, name, source = schedule.resolve_shift(date_str, day_name)
         lines.append(_format_shift_line(date, ext, name, source, is_today))
-        if source == "available":
+        if source == "available" and not is_past:
             open_shifts.append((date_str, "night"))
 
     blocks = [
@@ -89,14 +97,14 @@ def build_week_schedule(schedule, start_date: datetime | None = None) -> list[di
         elements = []
         for date_str, shift_type in open_shifts:
             dt = datetime.strptime(date_str, "%Y-%m-%d")
-            suffix = " (Day)" if shift_type == "day" else ""
+            label = "Day" if shift_type == "day" else "Night"
             action_suffix = "_day" if shift_type == "day" else ""
             elements.append(
                 {
                     "type": "button",
                     "text": {
                         "type": "plain_text",
-                        "text": f"Pick up {dt.strftime('%a %b %-d')}{suffix}",
+                        "text": f"Pick up {dt.strftime('%a %b %-d')} {label}",
                     },
                     "action_id": f"pickup_{date_str}{action_suffix}",
                     "style": "primary",
@@ -112,20 +120,26 @@ def build_week_schedule(schedule, start_date: datetime | None = None) -> list[di
 
 
 def build_shift_change_message(
-    user_id: str, date_str: str, action: str, ext: str, name: str
+    user_id: str,
+    date_str: str,
+    action: str,
+    ext: str,
+    name: str,
+    shift_type: str = "night",
 ) -> list[dict]:
     """Build a channel notification for a shift change."""
     dt = datetime.strptime(date_str, "%Y-%m-%d")
     day_label = dt.strftime("%A, %b %-d")
+    type_label = f" ({SHIFT_LABELS.get(shift_type, shift_type)})" if shift_type == "day" else ""
 
     if action == "picked_up":
-        text = f":white_check_mark: <@{user_id}> picked up the shift for *{day_label}* (Ext {ext})"
+        text = f":white_check_mark: <@{user_id}> picked up the *{day_label}*{type_label} shift (Ext {ext})"
     elif action == "dropped":
-        text = f":warning: <@{user_id}> dropped the shift for *{day_label}* — it's now *Available*"
+        text = f":warning: <@{user_id}> dropped the *{day_label}*{type_label} shift — it's now *Available*"
     elif action == "swapped":
-        text = f":arrows_counterclockwise: <@{user_id}> swapped into the shift for *{day_label}* (Ext {ext})"
+        text = f":arrows_counterclockwise: <@{user_id}> swapped into the *{day_label}*{type_label} shift (Ext {ext})"
     else:
-        text = f"Shift updated for *{day_label}*: {name} (Ext {ext})"
+        text = f"Shift updated for *{day_label}*{type_label}: {name} (Ext {ext})"
 
     return [{"type": "section", "text": {"type": "mrkdwn", "text": text}}]
 
diff --git a/src/slack-bot/app.py b/src/slack-bot/app.py
index 7a7bd25..f254b54 100644
--- a/src/slack-bot/app.py
+++ b/src/slack-bot/app.py
@@ -153,6 +153,15 @@ def create_app(
         user_id = body["user"]["id"]
         channel_id = body["channel"]["id"]
 
+        today_str = datetime.now(EASTERN).strftime("%Y-%m-%d")
+        if date_str < today_str:
+            client.chat_postEphemeral(
+                channel=channel_id,
+                user=user_id,
+                text="That shift has already passed and can't be picked up.",
+            )
+            return
+
         employee = schedule.get_employee_by_slack_id(user_id)
         if not employee:
             client.chat_postEphemeral(
@@ -177,7 +186,8 @@ def create_app(
             _update_3cx_routing(employee["extension"])
 
         blocks = build_shift_change_message(
-            user_id, date_str, "picked_up", employee["extension"], employee["name"]
+            user_id, date_str, "picked_up", employee["extension"], employee["name"],
+            shift_type=shift_type,
         )
         respond(
             response_type="in_channel",
@@ -345,6 +355,10 @@ def create_app(
             return
 
         date_str = date.strftime("%Y-%m-%d")
+        if date_str < datetime.now(EASTERN).strftime("%Y-%m-%d"):
+            respond(text="You can't pick up a shift in the past.")
+            return
+
         day_name = date.strftime("%A")
         ext, name, source = schedule.resolve_shift(date_str, day_name)
 
@@ -396,6 +410,10 @@ def create_app(
             return
 
         date_str = date.strftime("%Y-%m-%d")
+        if date_str < datetime.now(EASTERN).strftime("%Y-%m-%d"):
+            respond(text="You can't drop a shift in the past.")
+            return
+
         day_name = date.strftime("%A")
         ext, name, source = schedule.resolve_shift(date_str, day_name)