diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 90bc663..908b0a7 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -14,7 +14,7 @@ jobs:
       matrix:
         include:
           - go: 1.21.x
-          - go: 1.12.x
+          - go: 1.15.x
 
     name: Build Go ${{ matrix.go }}
     runs-on: ubuntu-latest
diff --git a/go.mod b/go.mod
index 0b5cb80..dee2a6f 100644
--- a/go.mod
+++ b/go.mod
@@ -1,9 +1,11 @@
 module github.com/restic/calens
 
-go 1.12
+go 1.15
 
 require (
+	github.com/Masterminds/semver/v3 v3.2.1
 	github.com/Masterminds/sprig/v3 v3.0.1
 	github.com/go-test/deep v1.0.1
 	github.com/spf13/pflag v1.0.5
+	github.com/stretchr/testify v1.8.4
 )
diff --git a/go.sum b/go.sum
index 7ef2294..5a17a77 100644
--- a/go.sum
+++ b/go.sum
@@ -1,7 +1,8 @@
 github.com/Masterminds/goutils v1.1.0 h1:zukEsf/1JZwCMgHiK3GZftabmxiCw4apj3a28RPBiVg=
 github.com/Masterminds/goutils v1.1.0/go.mod h1:8cTjp+g8YejhMuvIA5y2vz3BpJxksy863GQaJW2MFNU=
-github.com/Masterminds/semver/v3 v3.0.2 h1:tRi7ENs+AaOUCH+j6qwNQgPYfV26dX3JNonq+V4mhqc=
 github.com/Masterminds/semver/v3 v3.0.2/go.mod h1:VPu/7SZ7ePZ3QOrcuXROw5FAcLl4a0cBrbBpGY/8hQs=
+github.com/Masterminds/semver/v3 v3.2.1 h1:RN9w6+7QoMeJVGyfmbcgs28Br8cvmnucEXnY0rYXWg0=
+github.com/Masterminds/semver/v3 v3.2.1/go.mod h1:qvl/7zhW3nngYb5+80sSMF+FG2BjYrf8m9wsX0PNOMQ=
 github.com/Masterminds/sprig/v3 v3.0.1 h1:RuaOafp+8qOLUPX1lInLfUrLc1MEVbnz7a40RLoixKY=
 github.com/Masterminds/sprig/v3 v3.0.1/go.mod h1:Cp7HwZjmqKrC+Y7XqSJOU2yRvAJRGLiohfgz5ZJj8+4=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -26,9 +27,14 @@ github.com/spf13/cast v1.3.0/go.mod h1:Qx5cxh0v+4UWYiBimWS+eyWzqEqokIECu5etghLkU
 github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
 github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
+github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
-github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
+github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
+github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20190911031432-227b76d455e7 h1:0hQKqeLdqlt5iIwVOBErRisrHJAN57yOiPRQItI20fU=
 golang.org/x/crypto v0.0.0-20190911031432-227b76d455e7/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
@@ -40,3 +46,6 @@ gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/main.go b/main.go
index 42e5c61..9cc1cd4 100644
--- a/main.go
+++ b/main.go
@@ -16,6 +16,7 @@ import (
 
 	"text/template"
 
+	"github.com/Masterminds/semver/v3"
 	"github.com/Masterminds/sprig/v3"
 	"github.com/spf13/pflag"
 )
@@ -116,7 +117,7 @@ func (s ReleaseSlice) Swap(i, j int) {
 	s[i], s[j] = s[j], s[i]
 }
 
-var versionRegex = regexp.MustCompile(`^(\d+\.\d+\.\d+)(_(\d{4}-\d{2}-\d{2}))?$`)
+var versionRegex = regexp.MustCompile(`^([^_]+)(?:_(\d{4}-\d{2}-\d{2}))?$`)
 
 // readReleases lists the directory and parses all releases from the subdir
 // names there. A valid release subdir has the format "x.y.z_YYYY-MM-DD", the
@@ -159,12 +160,15 @@ func readReleases(dir string) (result []Release) {
 			continue
 		}
 
-		ver := data[1]
-		date := data[3]
+		ver, err := semver.NewVersion(data[1])
+		if err != nil {
+			die("invalid subdir name %v. Parsing semver returned error: %v", filepath.Join(dir, entry.Name()), err)
+		}
+		date := data[2]
 
 		rel := Release{
 			path:    filepath.Join(dir, entry.Name()),
-			Version: ver,
+			Version: ver.String(),
 		}
 
 		if date != "" {
diff --git a/main_test.go b/main_test.go
index bd86cd3..23a41cc 100644
--- a/main_test.go
+++ b/main_test.go
@@ -4,9 +4,12 @@ import (
 	"io/ioutil"
 	"net/url"
 	"os"
+	"path/filepath"
 	"testing"
+	"time"
 
 	"github.com/go-test/deep"
+	"github.com/stretchr/testify/assert"
 )
 
 func parseURL(t testing.TB, s string) *url.URL {
@@ -17,6 +20,10 @@ func parseURL(t testing.TB, s string) *url.URL {
 	return url
 }
 
+func ptrTime(v time.Time) *time.Time {
+	return &v
+}
+
 func TestReadFile(t *testing.T) {
 	var tests = []struct {
 		Data string
@@ -165,6 +172,36 @@ https://forum.restic.net/t/getting-last-successful-backup-time/531
 		})
 	}
 }
+func TestReadReleases(t *testing.T) {
+	type testData struct {
+		Date       *time.Time
+		FolderName string
+		Version    string
+	}
+	dir := t.TempDir()
+	releases := []testData{
+		{Date: nil, FolderName: "unreleased", Version: "unreleased"},
+		{Date: ptrTime(time.Date(2023, time.November, 12, 0, 0, 0, 0, time.UTC)), FolderName: "2.0.0-rc.1+build.12345_2023-11-12", Version: "2.0.0-rc.1+build.12345"},
+		{Date: ptrTime(time.Date(2023, time.November, 10, 0, 0, 0, 0, time.UTC)), FolderName: "0.0.1-rc.1_2023-11-10", Version: "0.0.1-rc.1"},
+		{Date: ptrTime(time.Date(2023, time.November, 10, 0, 0, 0, 0, time.UTC)), FolderName: "1.0.1_2023-11-10", Version: "1.0.1"},
+		{Date: ptrTime(time.Date(2023, time.November, 9, 0, 0, 0, 0, time.UTC)), FolderName: "4.0.0_2023-11-09", Version: "4.0.0"},
+		{Date: ptrTime(time.Date(2023, time.November, 8, 0, 0, 0, 0, time.UTC)), FolderName: "1.0.2-alpha.10_2023-11-08", Version: "1.0.2-alpha.10"},
+		{Date: ptrTime(time.Date(2023, time.September, 7, 0, 0, 0, 0, time.UTC)), FolderName: "1.0.0_2023-09-07", Version: "1.0.0"},
+		{Date: ptrTime(time.Date(2023, time.May, 1, 0, 0, 0, 0, time.UTC)), FolderName: "12.10.21_2023-05-01", Version: "12.10.21"},
+	}
+	for _, release := range releases {
+		err := os.Mkdir(filepath.Join(dir, release.FolderName), 0750)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+	parsedReleases := readReleases(dir)
+	// test the sorting and the parsing of the folder names
+	for i, parsedRelease := range parsedReleases {
+		assert.Equal(t, releases[i].Date, parsedRelease.Date)
+		assert.Equal(t, releases[i].Version, parsedRelease.Version)
+	}
+}
 
 func TestWrapIndent(t *testing.T) {
 	var tests = []struct {