diff --git a/besu/src/main/java/org/hyperledger/besu/cli/subcommands/blocks/BlocksSubCommand.java b/besu/src/main/java/org/hyperledger/besu/cli/subcommands/blocks/BlocksSubCommand.java
index d46ba39502..b17cad4f2a 100644
--- a/besu/src/main/java/org/hyperledger/besu/cli/subcommands/blocks/BlocksSubCommand.java
+++ b/besu/src/main/java/org/hyperledger/besu/cli/subcommands/blocks/BlocksSubCommand.java
@@ -40,6 +40,9 @@ import java.io.PrintStream;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
+import java.time.Clock;
+import java.time.Instant;
+import java.time.ZoneOffset;
 import java.util.Optional;
 
 import io.vertx.core.Vertx;
@@ -122,12 +125,18 @@ public class BlocksSubCommand implements Runnable {
 
     @Option(
         names = "--format",
-        hidden = true,
         description =
             "The type of data to be imported, possible values are: ${COMPLETION-CANDIDATES} (default: ${DEFAULT-VALUE}).",
         arity = "1..1")
     private final BlockImportFormat format = BlockImportFormat.RLP;
 
+    @Option(
+        names = "--start-time",
+        description =
+            "The timestamp in seconds of the first block for JSON imports. Subsequent blocks will be 1 second later. (default: current time)",
+        arity = "1..1")
+    private final Long startTime = System.currentTimeMillis() / 1000;
+
     @SuppressWarnings("unused")
     @Spec
     private CommandSpec spec;
@@ -141,7 +150,7 @@ public class BlocksSubCommand implements Runnable {
       checkNotNull(parentCommand.rlpBlockImporter);
       checkNotNull(parentCommand.jsonBlockImporterFactory);
 
-      Optional<MetricsService> metricsService = initMetrics(parentCommand);
+      final Optional<MetricsService> metricsService = initMetrics(parentCommand);
 
       try {
         // As blocksImportFile even if initialized as null is injected by PicoCLI and param is
@@ -182,6 +191,8 @@ public class BlocksSubCommand implements Runnable {
         return parentCommand
             .parentCommand
             .getControllerBuilder()
+            // set to mainnet genesis block so validation rules won't reject it.
+            .clock(Clock.fixed(Instant.ofEpochSecond(startTime), ZoneOffset.UTC))
             .miningParameters(getMiningParameters())
             .build();
       } catch (final Exception e) {
@@ -200,7 +211,7 @@ public class BlocksSubCommand implements Runnable {
     private <T> void importJsonBlocks(final BesuController<T> controller, final Path path)
         throws IOException {
 
-      JsonBlockImporter<T> importer = parentCommand.jsonBlockImporterFactory.get(controller);
+      final JsonBlockImporter<T> importer = parentCommand.jsonBlockImporterFactory.get(controller);
       final String jsonData = Files.readString(path);
       importer.importChain(jsonData);
     }
@@ -270,15 +281,13 @@ public class BlocksSubCommand implements Runnable {
 
       final BesuController<?> controller = createBesuController();
       try {
-        switch (format) {
-          case RLP:
-            exportRlpFormat(controller);
-            break;
-          default:
-            throw new ParameterException(
-                spec.commandLine(), "Unsupported format: " + format.toString());
+        if (format == BlockExportFormat.RLP) {
+          exportRlpFormat(controller);
+        } else {
+          throw new ParameterException(
+              spec.commandLine(), "Unsupported format: " + format.toString());
         }
-      } catch (IOException e) {
+      } catch (final IOException e) {
         throw new ExecutionException(
             spec.commandLine(), "An error occurred while exporting blocks.", e);
       } finally {
@@ -292,7 +301,7 @@ public class BlocksSubCommand implements Runnable {
 
     private void exportRlpFormat(final BesuController<?> controller) throws IOException {
       final ProtocolContext<?> context = controller.getProtocolContext();
-      RlpBlockExporter exporter =
+      final RlpBlockExporter exporter =
           parentCommand.rlpBlockExporterFactory.get(context.getBlockchain());
       exporter.exportBlocks(blocksExportFile, getStartBlock(), getEndBlock());
     }
@@ -339,11 +348,11 @@ public class BlocksSubCommand implements Runnable {
       }
 
       // Error if data directory is empty
-      Path databasePath =
+      final Path databasePath =
           Paths.get(
               parentCommand.parentCommand.dataDir().toAbsolutePath().toString(),
               BesuController.DATABASE_PATH);
-      File databaseDirectory = new File(databasePath.toString());
+      final File databaseDirectory = new File(databasePath.toString());
       if (!databaseDirectory.isDirectory() || databaseDirectory.list().length == 0) {
         // Empty data directory, nothing to export
         throw new CommandLine.ParameterException(
diff --git a/besu/src/test/java/org/hyperledger/besu/cli/subcommands/blocks/BlocksSubCommandTest.java b/besu/src/test/java/org/hyperledger/besu/cli/subcommands/blocks/BlocksSubCommandTest.java
index 656976d40f..9f8bdeec10 100644
--- a/besu/src/test/java/org/hyperledger/besu/cli/subcommands/blocks/BlocksSubCommandTest.java
+++ b/besu/src/test/java/org/hyperledger/besu/cli/subcommands/blocks/BlocksSubCommandTest.java
@@ -56,22 +56,18 @@ public class BlocksSubCommandTest extends CommandTestAbstract {
           + System.lineSeparator();
 
   private static final String EXPECTED_BLOCK_IMPORT_USAGE =
-      "Usage: besu blocks import [-hV] --from=<FILE>"
-          //      "Usage: besu blocks import [-hV] [--format=<format>] --from=<FILE>"
-          + System.lineSeparator()
-          + "This command imports blocks from a file into the database."
-          // Hide format for while JSON option is under development
-          //          + System.lineSeparator()
-          //          + "      --format=<format>   The type of data to be imported, possible values
-          // are: RLP,\n"
-          //          + "                            JSON (default: RLP)."
-          + System.lineSeparator()
-          + "      --from=<FILE>   File containing blocks to import."
-          + System.lineSeparator()
-          + "  -h, --help          Show this help message and exit."
-          + System.lineSeparator()
-          + "  -V, --version       Print version information and exit."
-          + System.lineSeparator();
+      "Usage: besu blocks import [-hV] [--format=<format>] --from=<FILE>\n"
+          + "                          [--start-time=<startTime>]\n"
+          + "This command imports blocks from a file into the database.\n"
+          + "      --format=<format>   The type of data to be imported, possible values are:\n"
+          + "                            RLP, JSON (default: RLP).\n"
+          + "      --from=<FILE>       File containing blocks to import.\n"
+          + "  -h, --help              Show this help message and exit.\n"
+          + "      --start-time=<startTime>\n"
+          + "                          The timestamp in seconds of the first block for JSON\n"
+          + "                            imports. Subsequent blocks will be 1 second later.\n"
+          + "                            (default: current time)\n"
+          + "  -V, --version           Print version information and exit.\n";
 
   private static final String EXPECTED_BLOCK_EXPORT_USAGE =
       "Usage: besu blocks export [-hV] [--end-block=<LONG>] [--start-block=<LONG>]"
@@ -138,7 +134,7 @@ public class BlocksSubCommandTest extends CommandTestAbstract {
   @Test
   public void callingBlockImportSubCommandHelpMustDisplayUsage() {
     parseCommand(BLOCK_SUBCOMMAND_NAME, BLOCK_IMPORT_SUBCOMMAND_NAME, "--help");
-    assertThat(commandOutput.toString()).isEqualToIgnoringWhitespace(EXPECTED_BLOCK_IMPORT_USAGE);
+    assertThat(commandOutput.toString()).isEqualTo(EXPECTED_BLOCK_IMPORT_USAGE);
     assertThat(commandErrorOutput.toString()).isEmpty();
   }