diff --git a/nag b/nag
index b2812b8..003b912 100755
--- a/nag
+++ b/nag
@@ -651,20 +651,20 @@ _next_for_rule() {
   _time_of_day="$(date -d "@${_timestamp}" +%H:%M:%S)"
 
   case "${_rule}" in
-    hourly)   printf "%s" "$((_timestamp + 3600))" ;;
-    daily)    date -d "$(date -d "@${_timestamp}" +%Y-%m-%d) + 1 day ${_time_of_day}" +%s ;;
-    weekly)   _next_matching_day "${_timestamp}" "${_time_of_day}" "$(date -d "@${_timestamp}" +%u)" ;;
+    hour)    printf "%s" "$((_timestamp + 3600))" ;;
+    day)     date -d "$(date -d "@${_timestamp}" +%Y-%m-%d) + 1 day ${_time_of_day}" +%s ;;
+    week)    _next_matching_day "${_timestamp}" "${_time_of_day}" "$(date -d "@${_timestamp}" +%u)" ;;
     weekday) _next_matching_day "${_timestamp}" "${_time_of_day}" "1 2 3 4 5" ;;
     weekend) _next_matching_day "${_timestamp}" "${_time_of_day}" "6 7" ;;
-    mon)    _next_matching_day "${_timestamp}" "${_time_of_day}" "1" ;;
-    tue)    _next_matching_day "${_timestamp}" "${_time_of_day}" "2" ;;
-    wed)    _next_matching_day "${_timestamp}" "${_time_of_day}" "3" ;;
-    thu)    _next_matching_day "${_timestamp}" "${_time_of_day}" "4" ;;
-    fri)    _next_matching_day "${_timestamp}" "${_time_of_day}" "5" ;;
-    sat)    _next_matching_day "${_timestamp}" "${_time_of_day}" "6" ;;
-    sun)    _next_matching_day "${_timestamp}" "${_time_of_day}" "7" ;;
-    monthly)  _next_month "${_timestamp}" "${_time_of_day}" ;;
-    yearly)   _next_year "${_timestamp}" "${_time_of_day}" ;;
+    mon)     _next_matching_day "${_timestamp}" "${_time_of_day}" "1" ;;
+    tue)     _next_matching_day "${_timestamp}" "${_time_of_day}" "2" ;;
+    wed)     _next_matching_day "${_timestamp}" "${_time_of_day}" "3" ;;
+    thu)     _next_matching_day "${_timestamp}" "${_time_of_day}" "4" ;;
+    fri)     _next_matching_day "${_timestamp}" "${_time_of_day}" "5" ;;
+    sat)     _next_matching_day "${_timestamp}" "${_time_of_day}" "6" ;;
+    sun)     _next_matching_day "${_timestamp}" "${_time_of_day}" "7" ;;
+    month)   _next_month "${_timestamp}" "${_time_of_day}" ;;
+    year)    _next_year "${_timestamp}" "${_time_of_day}" ;;
   esac
 }
 
@@ -1072,6 +1072,67 @@ stop() {
   printf "Stopped alarm %s.\\n" "${_target_id}"
 }
 
+# check #######################################################################
+
+describe "check" <<HEREDOC
+Usage:
+  ${_ME} check
+
+Description:
+  Fire expired alarms. Intended to be run by cron every minute.
+  Repeating alarms are rescheduled. One-shot alarms are removed.
+HEREDOC
+check() {
+  [[ -f "${_ALARMS_FILE}" ]] || return 0
+
+  _acquire_lock
+  _read_alarms
+
+  local -a _new_alarms=()
+  local _now
+  _now="$(date +%s)"
+  local _line
+
+  for _line in "${_ALARMS[@]:-}"
+  do
+    [[ -n "${_line}" ]] || continue
+
+    local _id _timestamp _rule _message
+    _id="$(_get_alarm_field "${_line}" 1)"
+    _timestamp="$(_get_alarm_field "${_line}" 2)"
+    _rule="$(_get_alarm_field "${_line}" 3)"
+    _message="$(_get_alarm_field "${_line}" 4)"
+
+    if (( _timestamp <= _now ))
+    then
+      # Fire it.
+      ${NAG_CMD} "nag" "${_message}" || _warn printf "Failed to notify: %s\\n" "${_message}"
+
+      if [[ -n "${_rule}" ]]
+      then
+        # Repeating: reschedule.
+        local _next_ts
+        _next_ts="$(_next_occurrence "${_rule}" "${_timestamp}")"
+        _new_alarms+=("$(printf "%s\t%s\t%s\t%s" "${_id}" "${_next_ts}" "${_rule}" "${_message}")")
+      fi
+      # One-shot: drop it (don't add to _new_alarms).
+    else
+      # Not expired — keep it.
+      _new_alarms+=("${_line}")
+    fi
+  done
+
+  if [[ "${#_new_alarms[@]}" -eq 0 ]]
+  then
+    _ALARMS=()
+    : > "${_ALARMS_FILE}"
+  else
+    _ALARMS=("${_new_alarms[@]}")
+    _write_alarms
+  fi
+  _release_lock
+}
+
 # at ##########################################################################
 
 describe "at" <<HEREDOC
diff --git a/test/nag.bats b/test/nag.bats
index f7e695e..c166a56 100644
--- a/test/nag.bats
+++ b/test/nag.bats
@@ -213,3 +213,94 @@ load test_helper
   [[ "${_first_line}" =~ "standup" ]]
   [[ "${_second_line}" =~ "take a break" ]]
 }
+
+# check #######################################################################
+
+# Helper: write a raw alarm line directly to the alarms file.
+write_alarm() {
+  mkdir -p "${NAG_DIR}"
+  printf "%s\\n" "$1" >> "${NAG_DIR}/alarms"
+}
+
+@test "check fires expired one-shot and removes it" {
+  local _past_ts=$(( $(date +%s) - 60 ))
+  write_alarm "$(printf "1\t%s\t\tpast alarm" "${_past_ts}")"
+
+  # Record what was fired.
+  local _fired="${NAG_DIR}/fired"
+  export NAG_CMD="${NAG_DIR}/recorder"
+  cat > "${NAG_CMD}" <<'SCRIPT'
+#!/usr/bin/env bash
+printf "%s\n" "$2" >> "${NAG_DIR}/fired"
+SCRIPT
+  chmod +x "${NAG_CMD}"
+
+  run "${_NAG}" check
+  [ "${status}" -eq 0 ]
+
+  # Alarm should have been removed.
+  [[ ! -s "${NAG_DIR}/alarms" ]] || [ "$(wc -l < "${NAG_DIR}/alarms")" -eq 0 ]
+
+  # Notification should have fired.
+  grep -q "past alarm" "${_fired}"
+}
+
+@test "check reschedules expired repeating alarm" {
+  local _past_ts=$(( $(date +%s) - 60 ))
+  write_alarm "$(printf "1\t%s\tday\tdaily alarm" "${_past_ts}")"
+
+  run "${_NAG}" check
+  [ "${status}" -eq 0 ]
+
+  # Alarm should still exist with a future timestamp.
+  [ -s "${NAG_DIR}/alarms" ]
+  local _new_ts
+  _new_ts="$(cut -f2 "${NAG_DIR}/alarms" | head -1)"
+  local _now
+  _now="$(date +%s)"
+  (( _new_ts > _now ))
+}
+
+@test "check does not fire future alarms" {
+  local _future_ts=$(( $(date +%s) + 3600 ))
+  write_alarm "$(printf "1\t%s\t\tfuture alarm" "${_future_ts}")"
+
+  run "${_NAG}" check
+  [ "${status}" -eq 0 ]
+
+  # Alarm should still be there, unchanged.
+  [ -s "${NAG_DIR}/alarms" ]
+  grep -q "future alarm" "${NAG_DIR}/alarms"
+}
+
+@test "check fires all missed alarms" {
+  local _past1=$(( $(date +%s) - 120 ))
+  local _past2=$(( $(date +%s) - 60 ))
+  write_alarm "$(printf "1\t%s\t\tmissed one" "${_past1}")"
+  write_alarm "$(printf "2\t%s\t\tmissed two" "${_past2}")"
+
+  local _fired="${NAG_DIR}/fired"
+  export NAG_CMD="${NAG_DIR}/recorder"
+  cat > "${NAG_CMD}" <<'SCRIPT'
+#!/usr/bin/env bash
+printf "%s\n" "$2" >> "${NAG_DIR}/fired"
+SCRIPT
+  chmod +x "${NAG_CMD}"
+
+  run "${_NAG}" check
+  [ "${status}" -eq 0 ]
+
+  # Both should have fired.
+  grep -q "missed one" "${_fired}"
+  grep -q "missed two" "${_fired}"
+
+  # Both should be removed (one-shots).
+  [[ ! -s "${NAG_DIR}/alarms" ]] || [ "$(wc -l < "${NAG_DIR}/alarms")" -eq 0 ]
+}
+
+@test "help check shows check usage" {
+  run "${_NAG}" help check
+  [ "${status}" -eq 0 ]
+  [[ "${output}" =~ "Usage:" ]]
+  [[ "${output}" =~ "check" ]]
+}