diff --git a/services/search/pkg/bleve/mtime_test.go b/services/search/pkg/bleve/mtime_test.go
index c29c83d9b8..2118662289 100644
--- a/services/search/pkg/bleve/mtime_test.go
+++ b/services/search/pkg/bleve/mtime_test.go
@@ -1,6 +1,10 @@
 package bleve_test
 
 import (
+	"time"
+
+	"github.com/opencloud-eu/opencloud/pkg/conversions"
+
 	bleveSearch "github.com/blevesearch/bleve/v2"
 	bquery "github.com/blevesearch/bleve/v2/search/query"
 	. "github.com/onsi/ginkgo/v2"
@@ -21,7 +25,7 @@ var _ = Describe("Mtime date range", func() {
 		idx, err := bleveSearch.NewMemOnly(m)
 		Expect(err).ToNot(HaveOccurred())
 
-		r := search.Resource{ID: "x", Document: content.Document{Name: "f", Mtime: "2026-03-15T12:00:00.123456789Z"}}
+		r := search.Resource{ID: "x", Document: content.Document{Name: "f", Mtime: conversions.ToPointer(time.Date(2026, 3, 15, 12, 0, 0, 123456789, time.UTC))}}
 		doc, err := mapping.PrepareForIndex(r, r.SearchFieldOverrides())
 		Expect(err).ToNot(HaveOccurred())
 		Expect(idx.Index(r.ID, doc)).To(Succeed())
diff --git a/services/search/pkg/content/basic.go b/services/search/pkg/content/basic.go
index 1499258c98..7ba8638a18 100644
--- a/services/search/pkg/content/basic.go
+++ b/services/search/pkg/content/basic.go
@@ -3,9 +3,9 @@ package content
 import (
 	"context"
 	"encoding/json"
-	"time"
 
 	storageProvider "github.com/cs3org/go-cs3apis/cs3/storage/provider/v1beta1"
+	"github.com/opencloud-eu/opencloud/pkg/conversions"
 	"github.com/opencloud-eu/opencloud/pkg/log"
 	"github.com/opencloud-eu/reva/v2/pkg/tags"
 	"github.com/opencloud-eu/reva/v2/pkg/utils"
@@ -54,7 +54,7 @@ func (b Basic) Extract(_ context.Context, ri *storageProvider.ResourceInfo) (Doc
 	}
 
 	if ri.Mtime != nil {
-		doc.Mtime = utils.TSToTime(ri.Mtime).UTC().Format(time.RFC3339Nano)
+		doc.Mtime = conversions.ToPointer(utils.TSToTime(ri.Mtime).UTC())
 	}
 
 	return doc, nil
diff --git a/services/search/pkg/content/basic_test.go b/services/search/pkg/content/basic_test.go
index 86832ed418..709202fc33 100644
--- a/services/search/pkg/content/basic_test.go
+++ b/services/search/pkg/content/basic_test.go
@@ -1,6 +1,10 @@
 package content_test
 
 import (
+	"time"
+
+	"github.com/opencloud-eu/opencloud/pkg/conversions"
+
 	"context"
 	"encoding/json"
 
@@ -69,11 +73,11 @@ var _ = Describe("Basic", func() {
 		It("RFC3339 mtime", func() {
 			for _, data := range []struct {
 				second uint64
-				expect string
+				expect *time.Time
 			}{
-				{second: 4000, expect: "1970-01-01T01:06:40Z"},
-				{second: 3000, expect: "1970-01-01T00:50:00Z"},
-				{expect: ""},
+				{second: 4000, expect: conversions.ToPointer(time.Unix(4000, 0).UTC())},
+				{second: 3000, expect: conversions.ToPointer(time.Unix(3000, 0).UTC())},
+				{},
 			} {
 				ri := &storageProvider.ResourceInfo{}
 
diff --git a/services/search/pkg/content/content.go b/services/search/pkg/content/content.go
index b162ccdcfc..a789847244 100644
--- a/services/search/pkg/content/content.go
+++ b/services/search/pkg/content/content.go
@@ -2,6 +2,7 @@ package content
 
 import (
 	"strings"
+	"time"
 
 	"github.com/bbalet/stopwords"
 	libregraph "github.com/opencloud-eu/libre-graph-api-go"
@@ -18,7 +19,7 @@ type Document struct {
 	Name      string                     `json:"Name"`
 	Content   string                     `json:"Content"`
 	Size      uint64                     `json:"Size"`
-	Mtime     string                     `json:"Mtime"`
+	Mtime     *time.Time                 `json:"Mtime"`
 	MimeType  string                     `json:"MimeType"`
 	Tags      []string                   `json:"Tags"`
 	Favorites []string                   `json:"Favorites"`
diff --git a/services/search/pkg/opensearch/backend_test.go b/services/search/pkg/opensearch/backend_test.go
index 9ad254f835..2fb55f03b6 100644
--- a/services/search/pkg/opensearch/backend_test.go
+++ b/services/search/pkg/opensearch/backend_test.go
@@ -91,6 +91,16 @@ func TestEngine_Upsert(t *testing.T) {
 
 		tc.Require.IndicesCount([]string{indexName}, nil, 1)
 	})
+
+	t.Run("upsert without mtime", func(t *testing.T) {
+		// content.Extract leaves Mtime nil when the resource info carries none
+		document := opensearchtest.Testdata.Resources.File
+		document.ID = "1$1!4"
+		document.Mtime = nil
+		require.NoError(t, backend.Upsert(document.ID, document))
+
+		tc.Require.IndicesCount([]string{indexName}, nil, 2)
+	})
 }
 
 func TestEngine_Move(t *testing.T) {
diff --git a/services/search/pkg/opensearch/internal/convert/opensearch.go b/services/search/pkg/opensearch/internal/convert/opensearch.go
index 1eef75ac88..01c662096c 100644
--- a/services/search/pkg/opensearch/internal/convert/opensearch.go
+++ b/services/search/pkg/opensearch/internal/convert/opensearch.go
@@ -3,7 +3,6 @@ package convert
 import (
 	"fmt"
 	"strings"
-	"time"
 
 	opensearchgoAPI "github.com/opensearch-project/opensearch-go/v4/opensearchapi"
 	"google.golang.org/protobuf/types/known/timestamppb"
@@ -86,8 +85,8 @@ func OpenSearchHitToMatch(hit opensearchgoAPI.SearchHit) (*searchMessage.Match,
 		},
 	}
 
-	if mtime, err := time.Parse(time.RFC3339, resource.Mtime); err == nil {
-		match.Entity.LastModifiedTime = &timestamppb.Timestamp{Seconds: mtime.Unix(), Nanos: int32(mtime.Nanosecond())}
+	if resource.Mtime != nil {
+		match.Entity.LastModifiedTime = timestamppb.New(*resource.Mtime)
 	}
 
 	return match, nil
diff --git a/services/search/pkg/search/search.go b/services/search/pkg/search/search.go
index a659169672..c0dac8fe99 100644
--- a/services/search/pkg/search/search.go
+++ b/services/search/pkg/search/search.go
@@ -72,10 +72,6 @@ var resourceFieldOverrides = sync.OnceValue(func() map[string]mapping.FieldOpts
 		"Tags":      {Analyzer: "lowercaseKeyword", IncludeInAll: &excludeFromAll},
 		"Favorites": {Analyzer: "lowercaseKeyword", IncludeInAll: &excludeFromAll},
 		"location":  {Type: mapping.TypeGeopoint},
-		// Mtime is stored as an RFC3339 string; type it as a date so mtime:>...
-		// range queries are chronological on both backends (bleve DateRangeQuery
-		// / OpenSearch date range), not a lexicographic keyword compare.
-		"Mtime": {Type: mapping.TypeDatetime},
 	}
 })