diff --git a/README.md b/README.md
index 218c1ed..65a3ace 100644
--- a/README.md
+++ b/README.md
@@ -79,7 +79,7 @@ AWS_S3_BUCKET_NAME="<xxx>"
 # that is expected to be bigger than the maximum difference of backups.
 # Valid values have a suffix of (s)econds, (m)inutes or (h)ours.
 
-# BACKUP_PRUNING_LEEWAY="10m"
+# BACKUP_PRUNING_LEEWAY="1m"
 
 # In case your target bucket or directory contains other files than the ones
 # managed by this container, you can limit the scope of rotation by setting
diff --git a/cmd/backup/main.go b/cmd/backup/main.go
index 16d7d72..5453f72 100644
--- a/cmd/backup/main.go
+++ b/cmd/backup/main.go
@@ -11,11 +11,9 @@ import (
 	"io"
 	"io/ioutil"
 	"os"
-	"os/exec"
 	"path"
 	"path/filepath"
 	"strconv"
-	"strings"
 	"time"
 
 	"github.com/docker/docker/api/types"
@@ -23,6 +21,7 @@ import (
 	"github.com/docker/docker/api/types/swarm"
 	"github.com/docker/docker/client"
 	"github.com/joho/godotenv"
+	"github.com/leekchan/timeutil"
 	minio "github.com/minio/minio-go/v7"
 	"github.com/minio/minio-go/v7/pkg/credentials"
 	"github.com/sirupsen/logrus"
@@ -54,6 +53,7 @@ type script struct {
 	archive    string
 	sources    string
 	passphrase string
+	now        time.Time
 }
 
 // lock opens a lockfile at the given location, keeping it locked until the
@@ -119,6 +119,8 @@ func (s *script) init() error {
 	s.archive = os.Getenv("BACKUP_ARCHIVE")
 	s.sources = os.Getenv("BACKUP_SOURCES")
 	s.passphrase = os.Getenv("GPG_PASSPHRASE")
+
+	s.now = time.Now()
 	return nil
 }
 
@@ -237,11 +239,7 @@ func (s *script) stopContainersAndRun(thunk func() error) error {
 // takeBackup creates a tar archive of the configured backup location and
 // saves it to disk.
 func (s *script) takeBackup() error {
-	outBytes, err := exec.Command("date", fmt.Sprintf("+%s", s.file)).Output()
-	if err != nil {
-		return fmt.Errorf("takeBackup: error formatting filename template: %w", err)
-	}
-	s.file = strings.TrimSpace(string(outBytes))
+	s.file = timeutil.Strftime(&s.now, s.file)
 	if err := targz.Compress(s.sources, s.file); err != nil {
 		return fmt.Errorf("takeBackup: error compressing backup folder: %w", err)
 	}
@@ -345,7 +343,7 @@ func (s *script) pruneOldBackups() error {
 	time.Sleep(sleepFor)
 
 	s.logger.Infof("Trying to prune backups older than %d days now.", retentionDays)
-	deadline := time.Now().AddDate(0, 0, -retentionDays)
+	deadline := s.now.AddDate(0, 0, -retentionDays)
 
 	if s.bucket != "" {
 		candidates := s.mc.ListObjects(s.ctx, s.bucket, minio.ListObjectsOptions{
diff --git a/entrypoint.sh b/entrypoint.sh
index 2469ee7..1258c08 100644
--- a/entrypoint.sh
+++ b/entrypoint.sh
@@ -17,7 +17,7 @@ BACKUP_FILENAME="${BACKUP_FILENAME:-backup-%Y-%m-%dT%H-%M-%S.tar.gz}"
 BACKUP_ARCHIVE="${BACKUP_ARCHIVE:-/archive}"
 
 BACKUP_RETENTION_DAYS="${BACKUP_RETENTION_DAYS:-}"
-BACKUP_PRUNING_LEEWAY="${BACKUP_PRUNING_LEEWAY:-10m}"
+BACKUP_PRUNING_LEEWAY="${BACKUP_PRUNING_LEEWAY:-1m}"
 BACKUP_PRUNING_PREFIX="${BACKUP_PRUNING_PREFIX:-}"
 BACKUP_STOP_CONTAINER_LABEL="${BACKUP_STOP_CONTAINER_LABEL:-true}"
 
diff --git a/go.mod b/go.mod
index 771befb..8ccfd39 100644
--- a/go.mod
+++ b/go.mod
@@ -5,7 +5,9 @@ go 1.17
 require (
 	github.com/docker/docker v20.10.8+incompatible
 	github.com/joho/godotenv v1.3.0
+	github.com/leekchan/timeutil v0.0.0-20150802142658-28917288c48d
 	github.com/minio/minio-go/v7 v7.0.12
+	github.com/sirupsen/logrus v1.8.1
 	github.com/walle/targz v0.0.0-20140417120357-57fe4206da5a
 	golang.org/x/crypto v0.0.0-20210817164053-32db794688a5
 )
@@ -32,7 +34,6 @@ require (
 	github.com/opencontainers/image-spec v1.0.1 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/rs/xid v1.2.1 // indirect
-	github.com/sirupsen/logrus v1.8.1 // indirect
 	golang.org/x/net v0.0.0-20210226172049-e18ecbb05110 // indirect
 	golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1 // indirect
 	golang.org/x/text v0.3.4 // indirect
diff --git a/go.sum b/go.sum
index 6e3eade..1bb1be4 100644
--- a/go.sum
+++ b/go.sum
@@ -401,6 +401,8 @@ github.com/kr/pretty v0.2.1/go.mod h1:ipq/a2n7PKx3OHsz4KJII5eveXtPO4qwEXGdVfWzfn
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
 github.com/kr/pty v1.1.5/go.mod h1:9r2w37qlBe7rQ6e1fg1S/9xpWHSnaqNdHD3WcMdbPDA=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
+github.com/leekchan/timeutil v0.0.0-20150802142658-28917288c48d h1:2puqoOQwi3Ai1oznMOsFIbifm6kIfJaLLyYzWD4IzTs=
+github.com/leekchan/timeutil v0.0.0-20150802142658-28917288c48d/go.mod h1:hO90vCP2x3exaSH58BIAowSKvV+0OsY21TtzuFGHON4=
 github.com/magiconair/properties v1.8.0/go.mod h1:PppfXfuXeibc/6YijjN8zIbojt8czPbwD3XqdrwzmxQ=
 github.com/mailru/easyjson v0.0.0-20190614124828-94de47d64c63/go.mod h1:C1wdFJiN94OJF2b5HbByQZoLdCWB1Yqtg26g4irojpc=
 github.com/mailru/easyjson v0.0.0-20190626092158-b2ccc519800e/go.mod h1:C1wdFJiN94OJF2b5HbByQZoLdCWB1Yqtg26g4irojpc=