diff --git a/api/handler/attributes.go b/api/handler/attributes.go
index da4f8d4..22ceffb 100644
--- a/api/handler/attributes.go
+++ b/api/handler/attributes.go
@@ -73,7 +73,7 @@ func (h *handler) GetObjectAttributesHandler(w http.ResponseWriter, r *http.Requ
 	ctx := r.Context()
 	reqInfo := middleware.GetReqInfo(ctx)
 
-	params, err := parseGetObjectAttributeArgs(r)
+	params, err := parseGetObjectAttributeArgs(r, h.reqLogger(ctx))
 	if err != nil {
 		h.logAndSendError(ctx, w, "invalid request", reqInfo, err)
 		return
@@ -145,7 +145,7 @@ func writeAttributesHeaders(h http.Header, info *data.ExtendedObjectInfo, isBuck
 	// x-amz-request-charged
 }
 
-func parseGetObjectAttributeArgs(r *http.Request) (*GetObjectAttributesArgs, error) {
+func parseGetObjectAttributeArgs(r *http.Request, log *zap.Logger) (*GetObjectAttributesArgs, error) {
 	res := &GetObjectAttributesArgs{
 		VersionID: r.URL.Query().Get(api.QueryVersionID),
 	}
@@ -178,8 +178,8 @@ func parseGetObjectAttributeArgs(r *http.Request) (*GetObjectAttributesArgs, err
 		}
 	}
 
-	res.Conditional, err = parseConditionalHeaders(r.Header)
-	return res, err
+	res.Conditional = parseConditionalHeaders(r.Header, log)
+	return res, nil
 }
 
 func encodeToObjectAttributesResponse(info *data.ObjectInfo, p *GetObjectAttributesArgs, md5Enabled bool) (*GetObjectAttributesResponse, error) {
diff --git a/api/handler/get.go b/api/handler/get.go
index c524dfc..11b8770 100644
--- a/api/handler/get.go
+++ b/api/handler/get.go
@@ -13,6 +13,7 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/errors"
 	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/layer"
 	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/middleware"
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/internal/logs"
 	"go.uber.org/zap"
 )
 
@@ -154,11 +155,7 @@ func (h *handler) GetObjectHandler(w http.ResponseWriter, r *http.Request) {
 		reqInfo = middleware.GetReqInfo(ctx)
 	)
 
-	conditional, err := parseConditionalHeaders(r.Header)
-	if err != nil {
-		h.logAndSendError(ctx, w, "could not parse request params", reqInfo, err)
-		return
-	}
+	conditional := parseConditionalHeaders(r.Header, h.reqLogger(ctx))
 
 	bktInfo, err := h.getBucketAndCheckOwner(r, reqInfo.BucketName)
 	if err != nil {
@@ -290,21 +287,24 @@ func checkPreconditions(info *data.ObjectInfo, args *conditionalArgs, md5Enabled
 	return nil
 }
 
-func parseConditionalHeaders(headers http.Header) (*conditionalArgs, error) {
-	var err error
+func parseConditionalHeaders(headers http.Header, log *zap.Logger) *conditionalArgs {
 	args := &conditionalArgs{
 		IfMatch:     data.UnQuote(headers.Get(api.IfMatch)),
 		IfNoneMatch: data.UnQuote(headers.Get(api.IfNoneMatch)),
 	}
 
-	if args.IfModifiedSince, err = parseHTTPTime(headers.Get(api.IfModifiedSince)); err != nil {
-		return nil, err
+	if httpTime, err := parseHTTPTime(headers.Get(api.IfModifiedSince)); err == nil {
+		args.IfModifiedSince = httpTime
+	} else {
+		log.Warn(logs.FailedToParseHTTPTime, zap.String(api.IfModifiedSince, headers.Get(api.IfModifiedSince)), zap.Error(err))
 	}
-	if args.IfUnmodifiedSince, err = parseHTTPTime(headers.Get(api.IfUnmodifiedSince)); err != nil {
-		return nil, err
+	if httpTime, err := parseHTTPTime(headers.Get(api.IfUnmodifiedSince)); err == nil {
+		args.IfUnmodifiedSince = httpTime
+	} else {
+		log.Warn(logs.FailedToParseHTTPTime, zap.String(api.IfUnmodifiedSince, headers.Get(api.IfUnmodifiedSince)), zap.Error(err))
 	}
 
-	return args, nil
+	return args
 }
 
 func parseHTTPTime(data string) (*time.Time, error) {
diff --git a/api/handler/head.go b/api/handler/head.go
index ba183d3..314adfe 100644
--- a/api/handler/head.go
+++ b/api/handler/head.go
@@ -36,11 +36,7 @@ func (h *handler) HeadObjectHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	conditional, err := parseConditionalHeaders(r.Header)
-	if err != nil {
-		h.logAndSendError(ctx, w, "could not parse request params", reqInfo, err)
-		return
-	}
+	conditional := parseConditionalHeaders(r.Header, h.reqLogger(ctx))
 
 	p := &layer.HeadObjectParams{
 		BktInfo:   bktInfo,
diff --git a/api/handler/head_test.go b/api/handler/head_test.go
index 4eebc8c..b6aec29 100644
--- a/api/handler/head_test.go
+++ b/api/handler/head_test.go
@@ -68,6 +68,16 @@ func TestConditionalHead(t *testing.T) {
 		api.IfModifiedSince: zeroTime.UTC().Format(http.TimeFormat),
 	}
 	headObject(t, tc, bktName, objName, headers, http.StatusNotModified)
+
+	headers = map[string]string{
+		api.IfUnmodifiedSince: zeroTime.UTC().Format(time.RFC3339), // invalid format, header is ignored
+	}
+	headObject(t, tc, bktName, objName, headers, http.StatusOK)
+
+	headers = map[string]string{
+		api.IfModifiedSince: objInfo.Created.Add(time.Minute).Format(time.RFC3339), // invalid format, header is ignored
+	}
+	headObject(t, tc, bktName, objName, headers, http.StatusOK)
 }
 
 func headObject(t *testing.T, tc *handlerContext, bktName, objName string, headers map[string]string, status int) {
diff --git a/api/handler/patch.go b/api/handler/patch.go
index a9e79bc..60efe3d 100644
--- a/api/handler/patch.go
+++ b/api/handler/patch.go
@@ -12,6 +12,7 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/errors"
 	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/layer"
 	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/middleware"
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/internal/logs"
 	"go.uber.org/zap"
 )
 
@@ -31,11 +32,7 @@ func (h *handler) PatchObjectHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	conditional, err := parsePatchConditionalHeaders(r.Header)
-	if err != nil {
-		h.logAndSendError(ctx, w, "could not parse conditional headers", reqInfo, err)
-		return
-	}
+	conditional := parsePatchConditionalHeaders(r.Header, h.reqLogger(ctx))
 
 	bktInfo, err := h.getBucketAndCheckOwner(r, reqInfo.BucketName)
 	if err != nil {
@@ -137,17 +134,18 @@ func (h *handler) PatchObjectHandler(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
-func parsePatchConditionalHeaders(headers http.Header) (*conditionalArgs, error) {
-	var err error
+func parsePatchConditionalHeaders(headers http.Header, log *zap.Logger) *conditionalArgs {
 	args := &conditionalArgs{
 		IfMatch: data.UnQuote(headers.Get(api.IfMatch)),
 	}
 
-	if args.IfUnmodifiedSince, err = parseHTTPTime(headers.Get(api.IfUnmodifiedSince)); err != nil {
-		return nil, err
+	if httpTime, err := parseHTTPTime(headers.Get(api.IfUnmodifiedSince)); err == nil {
+		args.IfUnmodifiedSince = httpTime
+	} else {
+		log.Warn(logs.FailedToParseHTTPTime, zap.String(api.IfUnmodifiedSince, headers.Get(api.IfUnmodifiedSince)), zap.Error(err))
 	}
 
-	return args, nil
+	return args
 }
 
 func parsePatchByteRange(rangeStr string, objSize uint64) (*layer.RangeParams, error) {
diff --git a/api/handler/patch_test.go b/api/handler/patch_test.go
index aa29423..33aa339 100644
--- a/api/handler/patch_test.go
+++ b/api/handler/patch_test.go
@@ -60,6 +60,13 @@ func TestPatch(t *testing.T) {
 				api.IfMatch:           etag,
 			},
 		},
+		{
+			name: "If-Unmodified-Since invalid format, header is ignored",
+			rng:  "bytes 0-2/*",
+			headers: map[string]string{
+				api.IfUnmodifiedSince: created.Add(-24 * time.Hour).Format(time.RFC3339),
+			},
+		},
 		{
 			name: "invalid range syntax",
 			rng:  "bytes 0-2",
diff --git a/internal/logs/logs.go b/internal/logs/logs.go
index 3da1255..f8047a2 100644
--- a/internal/logs/logs.go
+++ b/internal/logs/logs.go
@@ -177,4 +177,5 @@ const (
 	MultinetConfigWontBeUpdated                          = "multinet config won't be updated"
 	MultinetDialSuccess                                  = "multinet dial successful"
 	MultinetDialFail                                     = "multinet dial failed"
+	FailedToParseHTTPTime                                = "failed to parse http time, header is ignored"
 )