diff --git a/internal/lexicon/lexicon.go b/internal/lexicon/lexicon.go
index 227f3ea..0feb4b7 100644
--- a/internal/lexicon/lexicon.go
+++ b/internal/lexicon/lexicon.go
@@ -65,7 +65,7 @@ func mustLoad() lexiconFile {
 		"day_offsets", "weekdays", "weekdays_english", "months_genitive", "hours_spoken",
 		"not_place_after_v", "parts_of_day", "reminder_verbs", "half_hour",
 		"filler_particles", "task_done_words", "task_drop_words",
-		"confirm_yes", "confirm_no",
+		"confirm_yes", "confirm_no", "hour_units", "minute_units",
 	} {
 		s, ok := f.Sets[name]
 		if !ok || (len(s.Words) == 0 && len(s.Values) == 0) {
@@ -139,7 +139,40 @@ func TaskDropWords() []string { return words("task_drop_words") }
 // making the utterance a request of its own. A caller strips these (along with
 // the numbers and the other closed time sets) to see whether an utterance
 // carries any content beside the value it was asked for. See the set's note.
-func SlotValueFrame() []string { return words("slot_value_frame") }
+// The hour and the minute nouns are part of the frame and are kept in their own
+// sets, so there is one copy of each closed class rather than a copy per caller.
+func SlotValueFrame() []string {
+	out := words("slot_value_frame")
+	out = append(out, HourUnits()...)
+	out = append(out, MinuteUnits()...)
+	return out
+}
+
+// HourUnits returns every form of the hour noun, and MinuteUnits every form of
+// the minute noun. One home for each, because four router sets used to list the
+// hour and all four stopped at "часу" (V-609). A caller folding time words into
+// one set reads these; a caller asking about a single word reads IsHourUnit or
+// IsMinuteUnit.
+func HourUnits() []string { return words("hour_units") }
+
+// MinuteUnits — see HourUnits.
+func MinuteUnits() []string { return words("minute_units") }
+
+// IsHourUnit reports whether a word is the hour noun in any form.
+func IsHourUnit(word string) bool { return inSet("hour_units", word) }
+
+// IsMinuteUnit reports whether a word is the minute noun in any form.
+func IsMinuteUnit(word string) bool { return inSet("minute_units", word) }
+
+func inSet(set, word string) bool {
+	w := norm(word)
+	for _, s := range ru.Sets[set].Words {
+		if w == s {
+			return true
+		}
+	}
+	return false
+}
 
 // DialogueCancel returns the ways he calls off the request Maven is assembling.
 // Distinct from TaskDropWords, which abandons an item that already exists.
diff --git a/internal/lexicon/lexicon_ru_v1.json b/internal/lexicon/lexicon_ru_v1.json
index 608f0b2..8629c96 100644
--- a/internal/lexicon/lexicon_ru_v1.json
+++ b/internal/lexicon/lexicon_ru_v1.json
@@ -210,6 +210,20 @@
         "передумал", "передумала", "неактуально"
       ]
     },
+    "hour_units": {
+      "note": "Every form of the hour noun, Russian and English (V-609). One home for a closed class that four router sets used to list separately, and all four stopped at \"часу\": \"напомни к двум часам\" lost its hour and the reminder was left asking \"Когда?\". Russian declines, so the dative plural is as ordinary a way to say an hour as the accusative singular. A caller that folds time words into one set reads HourUnits; a caller asking about one word reads IsHourUnit.",
+      "words": [
+        "час", "часа", "часов", "часу", "часам", "часами", "часах",
+        "hour", "hours"
+      ]
+    },
+    "minute_units": {
+      "note": "Every form of the minute noun, Russian and English (V-609). Same class as hour_units one noun over, and it had the same gap: the dative plural \"минутам\" was missing everywhere \"минут\" and \"минуты\" were present.",
+      "words": [
+        "минута", "минуты", "минуту", "минут", "минуте", "минутам", "минутами", "минутах",
+        "minute", "minutes"
+      ]
+    },
     "slot_value_frame": {
       "note": "The words that can stand around a bare slot value without making the utterance a request of its own (Vikunja #560). Prepositions, hedges and the nouns a spoken time is built from: strip these, the numbers, the interrogatives, the filler particles and the other time sets, and whatever is left is the utterance's OWN content. \"а что если в 11:00\" leaves nothing and is an answer; \"какая сейчас погода в Риме\" leaves \"погода\" and \"Риме\" and is not. Closed because each part of it is closed — Russian has a fixed list of prepositions, and a clock is built from a fixed list of nouns. It is not a stopword list: a word goes in only if it can never be the thing he is asking about.",
       "words": [
@@ -217,10 +231,10 @@
         "at", "on", "in", "by", "to", "till", "until", "after", "before", "about", "for",
         "нет", "не", "да", "ага", "угу", "ой", "ох", "тогда", "лучше", "может", "можно", "наверное", "наверно", "пожалуй", "точнее", "скорее", "если", "пусть", "прости", "извини", "слушай", "значит", "как-то", "типа", "вообще-то",
         "no", "yes", "yeah", "ok", "okay", "sorry", "maybe", "actually", "rather", "then", "well",
-        "час", "часа", "часов", "часу", "часам", "минут", "минута", "минуты", "минуту", "минутах", "полдень", "полночь", "полдня",
+        "полдень", "полночь", "полдня",
         "утра", "утро", "утру", "дня", "день", "днями", "вечера", "вечер", "вечеру", "ночи", "ночь", "ночью",
         "сейчас", "теперь", "сегодняшний", "ближайший", "ближайшее",
-        "hour", "hours", "minute", "minutes", "noon", "midnight", "am", "pm", "oclock", "now"
+        "noon", "midnight", "am", "pm", "oclock", "now"
       ]
     },
     "dialogue_cancel": {
diff --git a/internal/router/dateparser.go b/internal/router/dateparser.go
index 15cd364..f15d44a 100644
--- a/internal/router/dateparser.go
+++ b/internal/router/dateparser.go
@@ -45,10 +45,10 @@ try:
     now = datetime.fromisoformat(sys.argv[2])
     # Pre-process: replace Russian time qualifiers with AM/PM.
     # Handles "9 утра", "10 часов утра", "3 часа дня" etc.
-    text = re.sub(r'(\d+)\s+(?:час(?:а|ов)?\s+)?утра\b', r'\1 am', text, flags=re.IGNORECASE)
-    text = re.sub(r'(\d+)\s+(?:час(?:а|ов)?\s+)?вечера\b', r'\1 pm', text, flags=re.IGNORECASE)
-    text = re.sub(r'(\d+)\s+(?:час(?:а|ов)?\s+)?дня\b', r'\1 pm', text, flags=re.IGNORECASE)
-    text = re.sub(r'(\d+)\s+(?:час(?:а|ов)?\s+)?ночи\b', r'\1 am', text, flags=re.IGNORECASE)
+    text = re.sub(r'(\d+)\s+(?:час(?:а|ов|у|ам)?\s+)?утра\b', r'\1 am', text, flags=re.IGNORECASE)
+    text = re.sub(r'(\d+)\s+(?:час(?:а|ов|у|ам)?\s+)?вечера\b', r'\1 pm', text, flags=re.IGNORECASE)
+    text = re.sub(r'(\d+)\s+(?:час(?:а|ов|у|ам)?\s+)?дня\b', r'\1 pm', text, flags=re.IGNORECASE)
+    text = re.sub(r'(\d+)\s+(?:час(?:а|ов|у|ам)?\s+)?ночи\b', r'\1 am', text, flags=re.IGNORECASE)
     # A bare hour after a preposition is dropped on the floor by dateparser:
     # "завтра в 7" resolves to tomorrow at the CURRENT clock, and "завтра в 7
     # часов" is read as seven hours from now. Only a qualifier (already an
@@ -56,7 +56,9 @@ try:
     # English "at 7" fails identically, so both prepositions are rewritten.
     # "на 9" is the same hour said with the other preposition, and it was not
     # read at all until V-579: "в 9" set the reminder and "на 9" did not.
-    text = re.sub(r'(?<![\w:])(в|во|на|at)\s+([01]?\d|2[0-3])(?:\s+час(?:а|ов)?)?(?![\d:.\w])',
+    # "к двум часам" is a third preposition and the dative that goes with it,
+    # and it was read as no time at all until V-609.
+    text = re.sub(r'(?<![\w:])(в|во|на|к|ко|at|by)\s+([01]?\d|2[0-3])(?:\s+час(?:а|ов|у|ам)?)?(?![\d:.\w])',
                   lambda m: '%s %02d:00' % (m.group(1), int(m.group(2))), text, flags=re.IGNORECASE)
     settings = {'PREFER_DATES_FROM': 'future', 'RELATIVE_BASE': now}
     # Two-step: search_dates finds the date substring in text,
diff --git a/internal/router/hourunit_test.go b/internal/router/hourunit_test.go
new file mode 100644
index 0000000..8f879a9
--- /dev/null
+++ b/internal/router/hourunit_test.go
@@ -0,0 +1,74 @@
+package router
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+// TestDativePluralHourIsAnHour — "напомни к двум часам позвонить маме" reached
+// the daemon with no time at all and she asked the open "Когда?", while "к трём"
+// one word over read fine (V-609). The word that lost it was "часам", the dative
+// plural of "час", which four separate hour sets in this package left out.
+func TestDativePluralHourIsAnHour(t *testing.T) {
+	const s = "напомни к двум часам позвонить маме"
+	if !MentionsTime(s) {
+		t.Errorf("MentionsTime(%q) = false; the sentence names two o'clock", s)
+	}
+	if !NamesAnHour(s) {
+		t.Errorf("NamesAnHour(%q) = false; the sentence names two o'clock", s)
+	}
+	if got, want := SpellOutDigits(s), "напомни к 2 часам позвонить маме"; got != want {
+		t.Errorf("SpellOutDigits(%q) = %q, want %q", s, got, want)
+	}
+	// The slot itself, which is what the daemon reads. It was empty, so
+	// whenGapOf named the hour missing and she asked "Когда?".
+	now := time.Date(2026, 8, 6, 3, 39, 0, 0, time.UTC)
+	ex := Extractor{Time: StubDateTimeParser{}}
+	got := ex.Extract(context.Background(), IntentReminder, s, now)
+	if !got.HasTime {
+		t.Fatalf("the hour was spoken, so the slot must be filled: %+v", got)
+	}
+	if h := got.Time.Hour(); h != 2 && h != 14 {
+		t.Errorf("fire time = %s, want two o'clock in one half of the day or the other", got.Time.Format("15:04"))
+	}
+}
+
+// TestHourUnitReachesEverySite — the four sets that read the hour noun now read
+// one lexicon key, so a form added there is a form all four know. "часам" is the
+// form that was missing from every one of them.
+func TestHourUnitReachesEverySite(t *testing.T) {
+	for _, w := range []string{"час", "часа", "часов", "часу", "часам"} {
+		if !numeralContext[w] {
+			t.Errorf("numeralContext is missing %q", w)
+		}
+		if !hourMarkers[w] {
+			t.Errorf("hourMarkers is missing %q", w)
+		}
+		if !timeMarkers[w] {
+			t.Errorf("timeMarkers is missing %q", w)
+		}
+		if _, ok := unitToDuration(2, w); !ok {
+			t.Errorf("unitToDuration does not know %q", w)
+		}
+	}
+}
+
+// TestMinuteUnitHasTheSameForms — the same defect one noun over: "минутам" was
+// missing everywhere "минут" and "минуты" were present.
+func TestMinuteUnitHasTheSameForms(t *testing.T) {
+	for _, w := range []string{"минут", "минуты", "минуту", "минутам"} {
+		if !numeralContext[w] {
+			t.Errorf("numeralContext is missing %q", w)
+		}
+		if !hourMarkers[w] {
+			t.Errorf("hourMarkers is missing %q", w)
+		}
+		if !timeMarkers[w] {
+			t.Errorf("timeMarkers is missing %q", w)
+		}
+		if _, ok := unitToDuration(20, w); !ok {
+			t.Errorf("unitToDuration does not know %q", w)
+		}
+	}
+}
diff --git a/internal/router/numwords.go b/internal/router/numwords.go
index 28ba9f7..7bbbd6b 100644
--- a/internal/router/numwords.go
+++ b/internal/router/numwords.go
@@ -34,12 +34,21 @@ func numeralDigit(word string) (string, bool) {
 // numeralContext — the words that make a numeral a time. A numeral is only
 // rewritten when one of these sits next to it, so "три яблока" in a note is
 // left alone and "в три часа" is not.
-var numeralContext = map[string]bool{
-	"в": true, "во": true, "к": true, "около": true, "на": true,
-	"часа": true, "часов": true, "час": true, "часу": true,
-	"утра": true, "вечера": true, "дня": true, "ночи": true,
-	"минут": true, "минуты": true, "минуту": true,
-	"at": true, "by": true,
+var numeralContext = buildNumeralContext()
+
+func buildNumeralContext() map[string]bool {
+	m := map[string]bool{
+		"в": true, "во": true, "к": true, "около": true, "на": true,
+		"утра": true, "вечера": true, "дня": true, "ночи": true,
+		"at": true, "by": true,
+	}
+	for _, w := range lexicon.HourUnits() {
+		m[w] = true
+	}
+	for _, w := range lexicon.MinuteUnits() {
+		m[w] = true
+	}
+	return m
 }
 
 // SpellOutDigits rewrites spoken numbers as digits so the date parsers see the
diff --git a/internal/router/slots.go b/internal/router/slots.go
index 15e8f02..9648931 100644
--- a/internal/router/slots.go
+++ b/internal/router/slots.go
@@ -175,10 +175,14 @@ func afterWord(s, w string) string {
 	return ""
 }
 
-// hourPrepositions — the words a spoken hour sits behind. Three, and no more:
+// hourPrepositions — the words a spoken hour sits behind. Five, and no more:
 // the lexicon's frame set is much wider, and a word goes in here only when the
 // number after it is an hour of the day rather than a count of anything.
-var hourPrepositions = map[string]bool{"в": true, "во": true, "на": true}
+//
+// "к" and "ко" joined the three on V-609. "напомни к двум часам" named an hour
+// and parsed to nothing, so the reminder reached the daemon with no time and she
+// asked the open question about an hour he had just said.
+var hourPrepositions = map[string]bool{"в": true, "во": true, "на": true, "к": true, "ко": true}
 
 // StubDateTimeParser — a tiny relative/absolute parser standing in for
 // `dateparser` until the i18n module lands. Handles "in Nh"/"in Nm"/"in Ns" and
@@ -398,10 +402,18 @@ func leadingWordNumber(s string) (int, string, bool) {
 }
 
 func unitToDuration(n int, unit string) (time.Duration, bool) {
-	switch unit {
-	case "h", "hour", "hours", "hr", "hrs":
+	// The hour and the minute nouns are closed classes with one home in the
+	// lexicon, and the list here used to be short of the oblique forms (V-609).
+	if lexicon.IsHourUnit(unit) {
 		return time.Duration(n) * time.Hour, true
-	case "m", "min", "mins", "minute", "minutes":
+	}
+	if lexicon.IsMinuteUnit(unit) {
+		return time.Duration(n) * time.Minute, true
+	}
+	switch unit {
+	case "h", "hr", "hrs":
+		return time.Duration(n) * time.Hour, true
+	case "m", "min", "mins":
 		return time.Duration(n) * time.Minute, true
 	case "s", "sec", "secs", "second", "seconds":
 		return time.Duration(n) * time.Second, true
@@ -409,10 +421,6 @@ func unitToDuration(n int, unit string) (time.Duration, bool) {
 	case "day", "days":
 		return time.Duration(n) * 24 * time.Hour, true
 	// Russian units (inflected forms)
-	case "час", "часа", "часов":
-		return time.Duration(n) * time.Hour, true
-	case "минута", "минуты", "минут":
-		return time.Duration(n) * time.Minute, true
 	case "день", "дня", "дней":
 		return time.Duration(n) * 24 * time.Hour, true
 	case "неделя", "недели", "недель":
diff --git a/internal/router/timementions.go b/internal/router/timementions.go
index b5dd9f3..fbe9067 100644
--- a/internal/router/timementions.go
+++ b/internal/router/timementions.go
@@ -206,12 +206,16 @@ var hourMarkers = buildHourMarkers()
 func buildHourMarkers() map[string]bool {
 	m := map[string]bool{
 		"утра": true, "вечера": true, "дня": true, "ночи": true,
-		"часа": true, "часов": true, "час": true, "часу": true,
-		"минут": true, "минуты": true, "минуту": true,
 		"через": true, "спустя": true, "полчаса": true,
 		"полдень": true, "полночь": true,
 		"am": true, "pm": true, "noon": true, "midnight": true, "in": true,
 	}
+	for _, w := range lexicon.HourUnits() {
+		m[w] = true
+	}
+	for _, w := range lexicon.MinuteUnits() {
+		m[w] = true
+	}
 	for _, w := range lexicon.PartsOfDay() {
 		m[w] = true
 	}
@@ -274,11 +278,15 @@ var timeMarkers = buildTimeMarkers()
 func buildTimeMarkers() map[string]bool {
 	m := map[string]bool{
 		"утра": true, "вечера": true, "дня": true, "ночи": true,
-		"часа": true, "часов": true, "час": true, "часу": true,
-		"минут": true, "минуты": true, "минуту": true,
 		"через": true, "полчаса": true, "сейчас": true,
 		"am": true, "pm": true, "noon": true, "midnight": true,
 	}
+	for _, w := range lexicon.HourUnits() {
+		m[w] = true
+	}
+	for _, w := range lexicon.MinuteUnits() {
+		m[w] = true
+	}
 	for _, w := range lexicon.PartsOfDay() {
 		m[w] = true
 	}