diff --git a/pkg/ccl/backupccl/restore_job.go b/pkg/ccl/backupccl/restore_job.go
index 393723efc45d..f6fef7f9649c 100644
--- a/pkg/ccl/backupccl/restore_job.go
+++ b/pkg/ccl/backupccl/restore_job.go
@@ -685,6 +685,15 @@ type restoreResumer struct {
 	settings *cluster.Settings
 	execCfg  *sql.ExecutorConfig
 
+	// canResetTableModificationTime is true if the cluster version is new enough.
+	// In release-20.1, any decoded table descriptor needed a populated
+	// modification time regardless of its version number. In 20.2 and later we've
+	// relaxed this requirement to allow version 1 descriptors to be serialized
+	// with a zero modification time.
+	//
+	// TODO(ajwerner): Remove in 21.1.
+	canResetTableModificationTime bool
+
 	testingKnobs struct {
 		// beforePublishingDescriptors is called right before publishing
 		// descriptors, after any data has been restored.
@@ -850,7 +859,10 @@ func createImportingDescriptors(
 
 	// Assign new IDs and privileges to the tables, and update all references to
 	// use the new IDs.
-	if err := RewriteTableDescs(mutableTables, details.DescriptorRewrites, details.OverrideDB); err != nil {
+	if err := RewriteTableDescs(
+		mutableTables, details.DescriptorRewrites, details.OverrideDB,
+		r.canResetTableModificationTime,
+	); err != nil {
 		return nil, nil, nil, err
 	}
 	tableDescs := make([]*descpb.TableDescriptor, len(mutableTables))
@@ -1052,6 +1064,8 @@ func (r *restoreResumer) Resume(
 ) error {
 	details := r.job.Details().(jobspb.RestoreDetails)
 	p := phs.(sql.PlanHookState)
+	r.canResetTableModificationTime = p.ExecCfg().Settings.Version.IsActive(
+		ctx, clusterversion.VersionLeasedDatabaseDescriptors)
 
 	backupManifests, latestBackupManifest, sqlDescs, err := loadBackupSQLDescs(
 		ctx, p, details, details.Encryption,
diff --git a/pkg/ccl/backupccl/restore_planning.go b/pkg/ccl/backupccl/restore_planning.go
index 1951d578b5e0..c9563d8ee945 100644
--- a/pkg/ccl/backupccl/restore_planning.go
+++ b/pkg/ccl/backupccl/restore_planning.go
@@ -16,6 +16,7 @@ import (
 
 	"github.com/cockroachdb/cockroach/pkg/ccl/storageccl"
 	"github.com/cockroachdb/cockroach/pkg/ccl/utilccl"
+	"github.com/cockroachdb/cockroach/pkg/clusterversion"
 	"github.com/cockroachdb/cockroach/pkg/jobs"
 	"github.com/cockroachdb/cockroach/pkg/jobs/jobspb"
 	"github.com/cockroachdb/cockroach/pkg/keys"
@@ -835,9 +836,17 @@ func maybeRewriteSchemaID(curSchemaID descpb.ID, descriptorRewrites DescRewriteM
 
 // RewriteTableDescs mutates tables to match the ID and privilege specified
 // in descriptorRewrites, as well as adjusting cross-table references to use the
-// new IDs. overrideDB can be specified to set database names in views.
+// new IDs. overrideDB can be specified to set database names in views. The
+// canResetModTime parameter is set based on the cluster version. It is unsafe
+// to reset the mod time in a mixed version state as 20.1 nodes expect the mod
+// time to be set on all descriptors which are deserialized, even at version 1.
+//
+// TODO(ajwerner): Remove canResetModTime in 21.1.
 func RewriteTableDescs(
-	tables []*tabledesc.Mutable, descriptorRewrites DescRewriteMap, overrideDB string,
+	tables []*tabledesc.Mutable,
+	descriptorRewrites DescRewriteMap,
+	overrideDB string,
+	canResetModTime bool,
 ) error {
 	for _, table := range tables {
 		tableRewrite, ok := descriptorRewrites[table.ID]
@@ -846,7 +855,9 @@ func RewriteTableDescs(
 		}
 		// Reset the version and modification time on this new descriptor.
 		table.Version = 1
-		table.ModificationTime = hlc.Timestamp{}
+		if canResetModTime {
+			table.ModificationTime = hlc.Timestamp{}
+		}
 
 		if table.IsView() && overrideDB != "" {
 			// restore checks that all dependencies are also being restored, but if
@@ -1496,7 +1507,13 @@ func doRestorePlan(
 
 	// We attempt to rewrite ID's in the collected type and table descriptors
 	// to catch errors during this process here, rather than in the job itself.
-	if err := RewriteTableDescs(tables, descriptorRewrites, intoDB); err != nil {
+	//
+	// TODO(ajwerner): Remove this version check in 21.1.
+	canResetModTime := p.ExecCfg().Settings.Version.IsActive(
+		ctx, clusterversion.VersionLeasedDatabaseDescriptors)
+	if err := RewriteTableDescs(
+		tables, descriptorRewrites, intoDB, canResetModTime,
+	); err != nil {
 		return err
 	}
 	if err := rewriteDatabaseDescs(databases, descriptorRewrites); err != nil {
diff --git a/pkg/ccl/importccl/import_stmt.go b/pkg/ccl/importccl/import_stmt.go
index 49659de420af..d14ce7c06958 100644
--- a/pkg/ccl/importccl/import_stmt.go
+++ b/pkg/ccl/importccl/import_stmt.go
@@ -976,8 +976,12 @@ func prepareNewTableDescsForIngestion(
 		}
 		seqVals[id] = tableDesc.SeqVal
 	}
-
-	if err := backupccl.RewriteTableDescs(newMutableTableDescriptors, tableRewrites, ""); err != nil {
+	// TODO(ajwerner): Remove this in 21.1.
+	canResetModTime := p.ExecCfg().Settings.Version.IsActive(
+		ctx, clusterversion.VersionLeasedDatabaseDescriptors)
+	if err := backupccl.RewriteTableDescs(
+		newMutableTableDescriptors, tableRewrites, "", canResetModTime,
+	); err != nil {
 		return nil, err
 	}