diff --git a/app/vlstorage/main.go b/app/vlstorage/main.go
index efd8dfc21..0a6c9b55a 100644
--- a/app/vlstorage/main.go
+++ b/app/vlstorage/main.go
@@ -39,13 +39,13 @@ func Init() {
 		logger.Panicf("BUG: Init() has been already called")
 	}
 
-	if retentionPeriod.Msecs < 24*3600*1000 {
+	if retentionPeriod.Duration() < 24*time.Hour {
 		logger.Fatalf("-retentionPeriod cannot be smaller than a day; got %s", retentionPeriod)
 	}
 	cfg := &logstorage.StorageConfig{
-		Retention:       time.Millisecond * time.Duration(retentionPeriod.Msecs),
+		Retention:       retentionPeriod.Duration(),
 		FlushInterval:   *inmemoryDataFlushInterval,
-		FutureRetention: time.Millisecond * time.Duration(futureRetention.Msecs),
+		FutureRetention: futureRetention.Duration(),
 		LogNewStreams:   *logNewStreams,
 		LogIngestedRows: *logIngestedRows,
 	}
diff --git a/app/vmstorage/main.go b/app/vmstorage/main.go
index d7381a9f9..eef298616 100644
--- a/app/vmstorage/main.go
+++ b/app/vmstorage/main.go
@@ -102,13 +102,13 @@ func Init(resetCacheIfNeeded func(mrs []storage.MetricRow)) {
 	mergeset.SetIndexBlocksCacheSize(cacheSizeIndexDBIndexBlocks.IntN())
 	mergeset.SetDataBlocksCacheSize(cacheSizeIndexDBDataBlocks.IntN())
 
-	if retentionPeriod.Msecs < 24*3600*1000 {
+	if retentionPeriod.Duration() < 24*time.Hour {
 		logger.Fatalf("-retentionPeriod cannot be smaller than a day; got %s", retentionPeriod)
 	}
 	logger.Infof("opening storage at %q with -retentionPeriod=%s", *DataPath, retentionPeriod)
 	startTime := time.Now()
 	WG = syncwg.WaitGroup{}
-	strg := storage.MustOpenStorage(*DataPath, retentionPeriod.Msecs, *maxHourlySeries, *maxDailySeries)
+	strg := storage.MustOpenStorage(*DataPath, retentionPeriod.Duration(), *maxHourlySeries, *maxDailySeries)
 	Storage = strg
 	initStaleSnapshotsRemover(strg)
 
@@ -380,10 +380,10 @@ func RequestHandler(w http.ResponseWriter, r *http.Request) bool {
 
 func initStaleSnapshotsRemover(strg *storage.Storage) {
 	staleSnapshotsRemoverCh = make(chan struct{})
-	if snapshotsMaxAge.Msecs <= 0 {
+	if snapshotsMaxAge.Duration() <= 0 {
 		return
 	}
-	snapshotsMaxAgeDur := time.Duration(snapshotsMaxAge.Msecs) * time.Millisecond
+	snapshotsMaxAgeDur := snapshotsMaxAge.Duration()
 	staleSnapshotsRemoverWG.Add(1)
 	go func() {
 		defer staleSnapshotsRemoverWG.Done()
diff --git a/lib/flagutil/duration.go b/lib/flagutil/duration.go
index 87d602c6e..d42e20831 100644
--- a/lib/flagutil/duration.go
+++ b/lib/flagutil/duration.go
@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"strconv"
 	"strings"
+	"time"
 
 	"github.com/VictoriaMetrics/metricsql"
 )
@@ -30,6 +31,11 @@ type Duration struct {
 	valueString string
 }
 
+// Duration convert to time.Duration.
+func (d *Duration) Duration() time.Duration {
+	return time.Millisecond * time.Duration(d.Msecs)
+}
+
 // String implements flag.Value interface
 func (d *Duration) String() string {
 	return d.valueString
diff --git a/lib/flagutil/duration_test.go b/lib/flagutil/duration_test.go
index bd26d47b8..b899c45a8 100644
--- a/lib/flagutil/duration_test.go
+++ b/lib/flagutil/duration_test.go
@@ -3,6 +3,7 @@ package flagutil
 import (
 	"strings"
 	"testing"
+	"time"
 )
 
 func TestDurationSetFailure(t *testing.T) {
@@ -59,3 +60,22 @@ func TestDurationSetSuccess(t *testing.T) {
 	f("1w", 7*24*3600*1000)
 	f("0.25y", 0.25*365*24*3600*1000)
 }
+
+func TestDurationDuration(t *testing.T) {
+	f := func(value string, expected time.Duration) {
+		t.Helper()
+		var d Duration
+		if err := d.Set(value); err != nil {
+			t.Fatalf("unexpected error in d.Set(%q): %s", value, err)
+		}
+		if d.Duration() != expected {
+			t.Fatalf("unexpected result; got %v; want %v", d.Duration().String(), expected.String())
+		}
+	}
+	f("0", 0)
+	f("1", 31*24*time.Hour)
+	f("1h", time.Hour)
+	f("1.5d", 1.5*24*time.Hour)
+	f("1w", 7*24*time.Hour)
+	f("0.25y", 0.25*365*24*time.Hour)
+}
diff --git a/lib/storage/index_db_test.go b/lib/storage/index_db_test.go
index 074613f33..742592b95 100644
--- a/lib/storage/index_db_test.go
+++ b/lib/storage/index_db_test.go
@@ -508,7 +508,7 @@ func TestIndexDB(t *testing.T) {
 
 	t.Run("serial", func(t *testing.T) {
 		const path = "TestIndexDB-serial"
-		s := MustOpenStorage(path, maxRetentionMsecs, 0, 0)
+		s := MustOpenStorage(path, retentionMax, 0, 0)
 
 		db := s.idb()
 		mns, tsids, err := testIndexDBGetOrCreateTSIDByName(db, metricGroups)
@@ -521,7 +521,7 @@ func TestIndexDB(t *testing.T) {
 
 		// Re-open the storage and verify it works as expected.
 		s.MustClose()
-		s = MustOpenStorage(path, maxRetentionMsecs, 0, 0)
+		s = MustOpenStorage(path, retentionMax, 0, 0)
 
 		db = s.idb()
 		if err := testIndexDBCheckTSIDByName(db, mns, tsids, false); err != nil {
@@ -534,7 +534,7 @@ func TestIndexDB(t *testing.T) {
 
 	t.Run("concurrent", func(t *testing.T) {
 		const path = "TestIndexDB-concurrent"
-		s := MustOpenStorage(path, maxRetentionMsecs, 0, 0)
+		s := MustOpenStorage(path, retentionMax, 0, 0)
 		db := s.idb()
 
 		ch := make(chan error, 3)
@@ -1429,7 +1429,7 @@ func TestMatchTagFilters(t *testing.T) {
 func TestIndexDBRepopulateAfterRotation(t *testing.T) {
 	r := rand.New(rand.NewSource(1))
 	path := "TestIndexRepopulateAfterRotation"
-	s := MustOpenStorage(path, msecsPerMonth, 1e5, 1e5)
+	s := MustOpenStorage(path, retentionMonth, 1e5, 1e5)
 
 	db := s.idb()
 	if db.generation == 0 {
@@ -1516,7 +1516,7 @@ func TestIndexDBRepopulateAfterRotation(t *testing.T) {
 
 func TestSearchTSIDWithTimeRange(t *testing.T) {
 	const path = "TestSearchTSIDWithTimeRange"
-	s := MustOpenStorage(path, maxRetentionMsecs, 0, 0)
+	s := MustOpenStorage(path, retentionMax, 0, 0)
 	db := s.idb()
 
 	is := db.getIndexSearch(noDeadline)
@@ -1966,7 +1966,7 @@ func newTestStorage() *Storage {
 		metricNameCache:   workingsetcache.New(1234),
 		tsidCache:         workingsetcache.New(1234),
 		dateMetricIDCache: newDateMetricIDCache(),
-		retentionMsecs:    maxRetentionMsecs,
+		retentionMsecs:    retentionMax.Milliseconds(),
 	}
 	s.setDeletedMetricIDs(&uint64set.Set{})
 	return s
diff --git a/lib/storage/index_db_timing_test.go b/lib/storage/index_db_timing_test.go
index 0a2c48c19..d67bebaa7 100644
--- a/lib/storage/index_db_timing_test.go
+++ b/lib/storage/index_db_timing_test.go
@@ -40,7 +40,7 @@ func BenchmarkRegexpFilterMismatch(b *testing.B) {
 
 func BenchmarkIndexDBAddTSIDs(b *testing.B) {
 	const path = "BenchmarkIndexDBAddTSIDs"
-	s := MustOpenStorage(path, maxRetentionMsecs, 0, 0)
+	s := MustOpenStorage(path, retentionMax, 0, 0)
 	db := s.idb()
 
 	const recordsPerLoop = 1e3
@@ -94,7 +94,7 @@ func BenchmarkHeadPostingForMatchers(b *testing.B) {
 	// This benchmark is equivalent to https://github.com/prometheus/prometheus/blob/23c0299d85bfeb5d9b59e994861553a25ca578e5/tsdb/head_bench_test.go#L52
 	// See https://www.robustperception.io/evaluating-performance-and-correctness for more details.
 	const path = "BenchmarkHeadPostingForMatchers"
-	s := MustOpenStorage(path, maxRetentionMsecs, 0, 0)
+	s := MustOpenStorage(path, retentionMax, 0, 0)
 	db := s.idb()
 
 	// Fill the db with data as in https://github.com/prometheus/prometheus/blob/23c0299d85bfeb5d9b59e994861553a25ca578e5/tsdb/head_bench_test.go#L66
@@ -261,7 +261,7 @@ func BenchmarkHeadPostingForMatchers(b *testing.B) {
 
 func BenchmarkIndexDBGetTSIDs(b *testing.B) {
 	const path = "BenchmarkIndexDBGetTSIDs"
-	s := MustOpenStorage(path, maxRetentionMsecs, 0, 0)
+	s := MustOpenStorage(path, retentionMax, 0, 0)
 	db := s.idb()
 
 	const recordsPerLoop = 1000
diff --git a/lib/storage/storage.go b/lib/storage/storage.go
index e61c0f0c0..9514ea8c9 100644
--- a/lib/storage/storage.go
+++ b/lib/storage/storage.go
@@ -33,8 +33,8 @@ import (
 )
 
 const (
-	msecsPerMonth     = 31 * 24 * 3600 * 1000
-	maxRetentionMsecs = 100 * 12 * msecsPerMonth
+	retentionMonth = 31 * 24 * time.Hour
+	retentionMax   = 100 * 12 * retentionMonth
 )
 
 // Storage represents TSDB storage.
@@ -154,21 +154,18 @@ type Storage struct {
 }
 
 // MustOpenStorage opens storage on the given path with the given retentionMsecs.
-func MustOpenStorage(path string, retentionMsecs int64, maxHourlySeries, maxDailySeries int) *Storage {
+func MustOpenStorage(path string, retention time.Duration, maxHourlySeries, maxDailySeries int) *Storage {
 	path, err := filepath.Abs(path)
 	if err != nil {
 		logger.Panicf("FATAL: cannot determine absolute path for %q: %s", path, err)
 	}
-	if retentionMsecs <= 0 {
-		retentionMsecs = maxRetentionMsecs
-	}
-	if retentionMsecs > maxRetentionMsecs {
-		retentionMsecs = maxRetentionMsecs
+	if retention <= 0 || retention > retentionMax {
+		retention = retentionMax
 	}
 	s := &Storage{
 		path:           path,
 		cachePath:      filepath.Join(path, cacheDirname),
-		retentionMsecs: retentionMsecs,
+		retentionMsecs: retention.Milliseconds(),
 		stop:           make(chan struct{}),
 	}
 	fs.MustMkdirIfNotExist(path)
@@ -246,7 +243,8 @@ func MustOpenStorage(path string, retentionMsecs int64, maxHourlySeries, maxDail
 
 	// Initialize nextRotationTimestamp
 	nowSecs := time.Now().UnixNano() / 1e9
-	nextRotationTimestamp := nextRetentionDeadlineSeconds(nowSecs, retentionMsecs/1000, retentionTimezoneOffsetSecs)
+	retentionSecs := retention.Milliseconds() / 1000 // not .Seconds() because unnecessary float64 conversion
+	nextRotationTimestamp := nextRetentionDeadlineSeconds(nowSecs, retentionSecs, retentionTimezoneOffsetSecs)
 	atomic.StoreInt64(&s.nextRotationTimestamp, nextRotationTimestamp)
 
 	// Load nextDayMetricIDs cache
diff --git a/lib/storage/storage_test.go b/lib/storage/storage_test.go
index a098fc72a..d2bfe3c71 100644
--- a/lib/storage/storage_test.go
+++ b/lib/storage/storage_test.go
@@ -478,15 +478,15 @@ func TestStorageOpenClose(t *testing.T) {
 
 func TestStorageRandTimestamps(t *testing.T) {
 	path := "TestStorageRandTimestamps"
-	retentionMsecs := int64(10 * msecsPerMonth)
-	s := MustOpenStorage(path, retentionMsecs, 0, 0)
+	retention := 10 * retentionMonth
+	s := MustOpenStorage(path, retention, 0, 0)
 	t.Run("serial", func(t *testing.T) {
 		for i := 0; i < 3; i++ {
 			if err := testStorageRandTimestamps(s); err != nil {
 				t.Fatalf("error on iteration %d: %s", i, err)
 			}
 			s.MustClose()
-			s = MustOpenStorage(path, retentionMsecs, 0, 0)
+			s = MustOpenStorage(path, retention, 0, 0)
 		}
 	})
 	t.Run("concurrent", func(t *testing.T) {
@@ -936,8 +936,8 @@ func testStorageRegisterMetricNames(s *Storage) error {
 func TestStorageAddRowsSerial(t *testing.T) {
 	rng := rand.New(rand.NewSource(1))
 	path := "TestStorageAddRowsSerial"
-	retentionMsecs := int64(msecsPerMonth * 10)
-	s := MustOpenStorage(path, retentionMsecs, 1e5, 1e5)
+	retention := 10 * retentionMonth
+	s := MustOpenStorage(path, retention, 1e5, 1e5)
 	if err := testStorageAddRows(rng, s); err != nil {
 		t.Fatalf("unexpected error: %s", err)
 	}
@@ -949,8 +949,8 @@ func TestStorageAddRowsSerial(t *testing.T) {
 
 func TestStorageAddRowsConcurrent(t *testing.T) {
 	path := "TestStorageAddRowsConcurrent"
-	retentionMsecs := int64(msecsPerMonth * 10)
-	s := MustOpenStorage(path, retentionMsecs, 1e5, 1e5)
+	retention := 10 * retentionMonth
+	s := MustOpenStorage(path, retention, 1e5, 1e5)
 	ch := make(chan error, 3)
 	for i := 0; i < cap(ch); i++ {
 		go func(n int) {
@@ -1164,8 +1164,8 @@ func testStorageAddMetrics(s *Storage, workerNum int) error {
 func TestStorageDeleteStaleSnapshots(t *testing.T) {
 	rng := rand.New(rand.NewSource(1))
 	path := "TestStorageDeleteStaleSnapshots"
-	retentionMsecs := int64(msecsPerMonth * 10)
-	s := MustOpenStorage(path, retentionMsecs, 1e5, 1e5)
+	retention := 10 * retentionMonth
+	s := MustOpenStorage(path, retention, 1e5, 1e5)
 	const rowsPerAdd = 1e3
 	const addsCount = 10
 	maxTimestamp := timestampFromTime(time.Now())
diff --git a/lib/storage/table_test.go b/lib/storage/table_test.go
index c664a55fe..49b2881ee 100644
--- a/lib/storage/table_test.go
+++ b/lib/storage/table_test.go
@@ -7,7 +7,7 @@ import (
 
 func TestTableOpenClose(t *testing.T) {
 	const path = "TestTableOpenClose"
-	const retentionMsecs = 123 * msecsPerMonth
+	const retention = 123 * retentionMonth
 
 	if err := os.RemoveAll(path); err != nil {
 		t.Fatalf("cannot remove %q: %s", path, err)
@@ -18,7 +18,7 @@ func TestTableOpenClose(t *testing.T) {
 
 	// Create a new table
 	strg := newTestStorage()
-	strg.retentionMsecs = retentionMsecs
+	strg.retentionMsecs = retention.Milliseconds()
 	tb := mustOpenTable(path, strg)
 
 	// Close it