diff --git a/llvm/include/llvm/Object/MachO.h b/llvm/include/llvm/Object/MachO.h
--- a/llvm/include/llvm/Object/MachO.h
+++ b/llvm/include/llvm/Object/MachO.h
@@ -880,6 +880,8 @@
   return OwningObject;
 }
 
+bool isMacho(const MemoryBuffer &Buffer);
+
 } // end namespace object
 } // end namespace llvm
 
diff --git a/llvm/lib/ObjCopy/Archive.cpp b/llvm/lib/ObjCopy/Archive.cpp
--- a/llvm/lib/ObjCopy/Archive.cpp
+++ b/llvm/lib/ObjCopy/Archive.cpp
@@ -11,6 +11,7 @@
 #include "llvm/ObjCopy/MultiFormatConfig.h"
 #include "llvm/ObjCopy/ObjCopy.h"
 #include "llvm/Object/Error.h"
+#include "llvm/Object/MachO.h"
 #include "llvm/Support/FileOutputBuffer.h"
 #include "llvm/Support/SmallVectorMemoryBuffer.h"
 
@@ -61,6 +62,10 @@
                               ArrayRef<NewArchiveMember> NewMembers,
                               bool WriteSymtab, object::Archive::Kind Kind,
                               bool Deterministic, bool Thin) {
+  if (Kind == object::Archive::K_BSD && !NewMembers.empty() &&
+      isMacho(*NewMembers.front().Buf))
+    Kind = object::Archive::K_DARWIN;
+
   if (Error E = writeArchive(ArcName, NewMembers, WriteSymtab, Kind,
                              Deterministic, Thin))
     return createFileError(ArcName, std::move(E));
diff --git a/llvm/lib/ObjCopy/MachO/MachOObjcopy.cpp b/llvm/lib/ObjCopy/MachO/MachOObjcopy.cpp
--- a/llvm/lib/ObjCopy/MachO/MachOObjcopy.cpp
+++ b/llvm/lib/ObjCopy/MachO/MachOObjcopy.cpp
@@ -484,9 +484,13 @@
           createNewArchiveMembers(Config, **ArOrErr);
       if (!NewArchiveMembersOrErr)
         return NewArchiveMembersOrErr.takeError();
+      auto Kind = (*ArOrErr)->kind();
+      if (Kind == object::Archive::K_BSD && !NewArchiveMembersOrErr->empty() &&
+          isMacho(*NewArchiveMembersOrErr->front().Buf))
+        Kind = object::Archive::K_DARWIN;
       Expected<std::unique_ptr<MemoryBuffer>> OutputBufferOrErr =
           writeArchiveToBuffer(*NewArchiveMembersOrErr,
-                               (*ArOrErr)->hasSymbolTable(), (*ArOrErr)->kind(),
+                               (*ArOrErr)->hasSymbolTable(), Kind,
                                Config.getCommonConfig().DeterministicArchives,
                                (*ArOrErr)->isThin());
       if (!OutputBufferOrErr)
diff --git a/llvm/lib/Object/MachOObjectFile.cpp b/llvm/lib/Object/MachOObjectFile.cpp
--- a/llvm/lib/Object/MachOObjectFile.cpp
+++ b/llvm/lib/Object/MachOObjectFile.cpp
@@ -21,7 +21,9 @@
 #include "llvm/ADT/Twine.h"
 #include "llvm/BinaryFormat/MachO.h"
 #include "llvm/BinaryFormat/Swift.h"
+#include "llvm/IR/LLVMContext.h"
 #include "llvm/Object/Error.h"
+#include "llvm/Object/IRObjectFile.h"
 #include "llvm/Object/MachO.h"
 #include "llvm/Object/ObjectFile.h"
 #include "llvm/Object/SymbolicFile.h"
@@ -5028,3 +5030,63 @@
     return false;
   }
 }
+
+namespace llvm {
+namespace object {
+
+bool isMacho(const MemoryBuffer &Buffer) {
+  auto Magic = identify_magic(Buffer.getBuffer());
+  switch (Magic) {
+  case file_magic::bitcode: {
+    LLVMContext Context;
+    if (auto ObjOrErr = object::SymbolicFile::createSymbolicFile(
+            Buffer, file_magic::bitcode, &Context, false)) {
+      auto &IRObject = cast<object::IRObjectFile>(**ObjOrErr);
+      return Triple(IRObject.getTargetTriple()).isOSDarwin();
+    } else {
+      // Squelch the error in case this was not a SymbolicFile.
+      consumeError(ObjOrErr.takeError());
+    }
+
+    return false;
+  }
+  case file_magic::macho_bundle:
+  case file_magic::macho_core:
+  case file_magic::macho_dsym_companion:
+  case file_magic::macho_dynamic_linker:
+  case file_magic::macho_dynamically_linked_shared_lib:
+  case file_magic::macho_dynamically_linked_shared_lib_stub:
+  case file_magic::macho_executable:
+  case file_magic::macho_fixed_virtual_memory_shared_lib:
+  case file_magic::macho_kext_bundle:
+  case file_magic::macho_object:
+  case file_magic::macho_preload_executable:
+  case file_magic::macho_universal_binary:
+    return true;
+  case file_magic::archive:
+  case file_magic::coff_cl_gl_object:
+  case file_magic::coff_import_library:
+  case file_magic::coff_object:
+  case file_magic::cuda_fatbinary:
+  case file_magic::dxcontainer_object:
+  case file_magic::elf:
+  case file_magic::elf_core:
+  case file_magic::elf_executable:
+  case file_magic::elf_relocatable:
+  case file_magic::elf_shared_object:
+  case file_magic::goff_object:
+  case file_magic::minidump:
+  case file_magic::pdb:
+  case file_magic::pecoff_executable:
+  case file_magic::tapi_file:
+  case file_magic::unknown:
+  case file_magic::wasm_object:
+  case file_magic::windows_resource:
+  case file_magic::xcoff_object_32:
+  case file_magic::xcoff_object_64:
+    return false;
+  }
+}
+
+} // namespace object
+} // namespace llvm
diff --git a/llvm/test/tools/llvm-ar/macho-edit.test b/llvm/test/tools/llvm-ar/macho-edit.test
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/llvm-ar/macho-edit.test
@@ -0,0 +1,14 @@
+# REQUIRES: x86-registered-target
+
+## Make sure darwin specific timestamps are preserved when updating the archive
+
+# RUN: rm -rf %t; mkdir -p %t/a %t/b
+# RUN: yaml2obj %p/Inputs/macho.yaml > %t/a/dup.o
+# RUN: yaml2obj %p/Inputs/macho.yaml > %t/b/dup.o
+# RUN: yaml2obj %p/Inputs/macho.yaml > %t/last.o
+
+# RUN: llvm-ar --format=darwin crD %t/lib.a %t/a/dup.o %t/b/dup.o %t/last.o
+# RUN: cp %t/lib.a %t/originallib.a
+## Inserting existing object is ignored but forces llvm-ar to rewrite the archive
+# RUN: llvm-ar crD %t/lib.a %t/last.o
+# RUN: cmp %t/lib.a %t/originallib.a
diff --git a/llvm/test/tools/llvm-objcopy/MachO/archive-format.test b/llvm/test/tools/llvm-objcopy/MachO/archive-format.test
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/llvm-objcopy/MachO/archive-format.test
@@ -0,0 +1,10 @@
+## Make sure darwin specific timestamp logic is preserved in archives
+
+# RUN: rm -rf %t; mkdir -p %t/a %t/b
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %p/Inputs/macho.64.s -o %t/a/dup.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %p/Inputs/macho.64.s -o %t/b/dup.o
+# RUN: llvm-ar --format=darwin crD %t/lib.a %t/a/dup.o %t/b/dup.o
+# RUN: llvm-objcopy %t/lib.a %t/lib.copy.a
+# RUN: cmp %t/lib.a %t/lib.copy.a
+
+# REQUIRES: x86-registered-target
diff --git a/llvm/test/tools/llvm-objcopy/MachO/universal-object.test b/llvm/test/tools/llvm-objcopy/MachO/universal-object.test
--- a/llvm/test/tools/llvm-objcopy/MachO/universal-object.test
+++ b/llvm/test/tools/llvm-objcopy/MachO/universal-object.test
@@ -12,9 +12,9 @@
 # RUN: cmp %t.i386 %t.i386.copy
 # RUN: cmp %t.x86_64 %t.x86_64.copy
 
-## Case 2: copy a universal object file containing an archive.
+## Case 2: copy a universal object file containing an archive with darwin specific timestamps.
 # RUN: rm -f %t.archive.i386
-# RUN: llvm-ar --format=gnu cr %t.archive.i386 %t.i386
+# RUN: llvm-ar --format=darwin cr %t.archive.i386 %t.i386 %t.i386
 # RUN: llvm-lipo %t.archive.i386 %t.x86_64 -create -output %t.universal.containing.archive
 # RUN: llvm-objcopy %t.universal.containing.archive %t.universal.containing.archive.copy
 # RUN: llvm-lipo %t.universal.containing.archive.copy -archs | FileCheck --check-prefix=VERIFY_ARCHS %s
diff --git a/llvm/tools/llvm-ar/llvm-ar.cpp b/llvm/tools/llvm-ar/llvm-ar.cpp
--- a/llvm/tools/llvm-ar/llvm-ar.cpp
+++ b/llvm/tools/llvm-ar/llvm-ar.cpp
@@ -970,6 +970,15 @@
     llvm_unreachable("");
   }
 
+  if (Kind == object::Archive::K_BSD) {
+    if (NewMembersP && !NewMembersP->empty() &&
+        llvm::object::isMacho(*NewMembersP->front().Buf))
+      Kind = object::Archive::K_DARWIN;
+    else if (!NewMembers.empty() &&
+             llvm::object::isMacho(*NewMembers.front().Buf))
+      Kind = object::Archive::K_DARWIN;
+  }
+
   Error E =
       writeArchive(ArchiveName, NewMembersP ? *NewMembersP : NewMembers, Symtab,
                    Kind, Deterministic, Thin, std::move(OldArchiveBuf));