Index: lld/trunk/COFF/DriverUtils.cpp
===================================================================
--- lld/trunk/COFF/DriverUtils.cpp
+++ lld/trunk/COFF/DriverUtils.cpp
@@ -718,7 +718,8 @@
   }
 
   Expected<std::unique_ptr<MemoryBuffer>> E =
-      llvm::object::writeWindowsResourceCOFF(Config->Machine, Parser);
+      llvm::object::writeWindowsResourceCOFF(Config->Machine, Parser,
+                                             Config->Timestamp);
   if (!E)
     fatal("failed to write .res to COFF: " + toString(E.takeError()));
 
Index: llvm/trunk/include/llvm/Object/WindowsResource.h
===================================================================
--- llvm/trunk/include/llvm/Object/WindowsResource.h
+++ llvm/trunk/include/llvm/Object/WindowsResource.h
@@ -232,7 +232,8 @@
 
 Expected<std::unique_ptr<MemoryBuffer>>
 writeWindowsResourceCOFF(llvm::COFF::MachineTypes MachineType,
-                         const WindowsResourceParser &Parser);
+                         const WindowsResourceParser &Parser,
+                         uint32_t TimeDateStamp);
 
 void printResourceTypeName(uint16_t TypeID, raw_ostream &OS);
 } // namespace object
Index: llvm/trunk/lib/Object/WindowsResource.cpp
===================================================================
--- llvm/trunk/lib/Object/WindowsResource.cpp
+++ llvm/trunk/lib/Object/WindowsResource.cpp
@@ -400,13 +400,13 @@
 public:
   WindowsResourceCOFFWriter(COFF::MachineTypes MachineType,
                             const WindowsResourceParser &Parser, Error &E);
-  std::unique_ptr<MemoryBuffer> write();
+  std::unique_ptr<MemoryBuffer> write(uint32_t TimeDateStamp);
 
 private:
   void performFileLayout();
   void performSectionOneLayout();
   void performSectionTwoLayout();
-  void writeCOFFHeader();
+  void writeCOFFHeader(uint32_t TimeDateStamp);
   void writeFirstSectionHeader();
   void writeSecondSectionHeader();
   void writeFirstSection();
@@ -499,17 +499,11 @@
   FileSize = alignTo(FileSize, SECTION_ALIGNMENT);
 }
 
-static std::time_t getTime() {
-  std::time_t Now = time(nullptr);
-  if (Now < 0 || !isUInt<32>(Now))
-    return UINT32_MAX;
-  return Now;
-}
-
-std::unique_ptr<MemoryBuffer> WindowsResourceCOFFWriter::write() {
+std::unique_ptr<MemoryBuffer>
+WindowsResourceCOFFWriter::write(uint32_t TimeDateStamp) {
   BufferStart = OutputBuffer->getBufferStart();
 
-  writeCOFFHeader();
+  writeCOFFHeader(TimeDateStamp);
   writeFirstSectionHeader();
   writeSecondSectionHeader();
   writeFirstSection();
@@ -520,16 +514,17 @@
   return std::move(OutputBuffer);
 }
 
-void WindowsResourceCOFFWriter::writeCOFFHeader() {
+void WindowsResourceCOFFWriter::writeCOFFHeader(uint32_t TimeDateStamp) {
   // Write the COFF header.
   auto *Header = reinterpret_cast<coff_file_header *>(BufferStart);
   Header->Machine = MachineType;
   Header->NumberOfSections = 2;
-  Header->TimeDateStamp = getTime();
+  Header->TimeDateStamp = TimeDateStamp;
   Header->PointerToSymbolTable = SymbolTableOffset;
   // One symbol for every resource plus 2 for each section and @feat.00
   Header->NumberOfSymbols = Data.size() + 5;
   Header->SizeOfOptionalHeader = 0;
+  // cvtres.exe sets 32BIT_MACHINE even for 64-bit machine types. Match it.
   Header->Characteristics = COFF::IMAGE_FILE_32BIT_MACHINE;
 }
 
@@ -794,12 +789,13 @@
 
 Expected<std::unique_ptr<MemoryBuffer>>
 writeWindowsResourceCOFF(COFF::MachineTypes MachineType,
-                         const WindowsResourceParser &Parser) {
+                         const WindowsResourceParser &Parser,
+                         uint32_t TimeDateStamp) {
   Error E = Error::success();
   WindowsResourceCOFFWriter Writer(MachineType, Parser, E);
   if (E)
     return std::move(E);
-  return Writer.write();
+  return Writer.write(TimeDateStamp);
 }
 
 } // namespace object
Index: llvm/trunk/test/tools/llvm-cvtres/help.test
===================================================================
--- llvm/trunk/test/tools/llvm-cvtres/help.test
+++ llvm/trunk/test/tools/llvm-cvtres/help.test
@@ -10,4 +10,5 @@
 ; HELP_TEST-DAG:    /NOLOGO        
 ; HELP_TEST-NEXT:   /OUT:filename  
 ; HELP_TEST-NEXT:   /READONLY      
+; HELP_TEST-NEXT:   /TIMESTAMP:<value> Timestamp for coff header, defaults to current time
 ; HELP_TEST-NEXT:   /VERBOSE
Index: llvm/trunk/test/tools/llvm-cvtres/timestamp.test
===================================================================
--- llvm/trunk/test/tools/llvm-cvtres/timestamp.test
+++ llvm/trunk/test/tools/llvm-cvtres/timestamp.test
@@ -0,0 +1,10 @@
+RUN: llvm-cvtres /timestamp:0x12345678 /out:%t %p/Inputs/test_resource.res
+RUN: llvm-readobj -h %t | FileCheck %s --check-prefix=1TO8
+
+1TO8: TimeDateStamp: 1979-09-05 22:51:36 (0x12345678)
+
+
+RUN: not llvm-cvtres /timestamp:0x123456789 /out:%t \
+RUN:     %p/Inputs/test_resource.res 2>&1 | FileCheck %s --check-prefix=ERR
+
+ERR: invalid timestamp: 0x123456789.  Expected 32-bit integer
Index: llvm/trunk/tools/llvm-cvtres/Opts.td
===================================================================
--- llvm/trunk/tools/llvm-cvtres/Opts.td
+++ llvm/trunk/tools/llvm-cvtres/Opts.td
@@ -12,3 +12,8 @@
 def HELP : Flag<["/", "-"], "HELP">;
 def H : Flag<["/", "-"], "H">, Alias<HELP>;
 def HELP_Q : Flag<["/?", "-?"], "">, Alias<HELP>;
+
+// Extensions.
+
+def TIMESTAMP : Joined<["/", "-"], "TIMESTAMP:">,
+    HelpText<"Timestamp for coff header, defaults to current time">;
Index: llvm/trunk/tools/llvm-cvtres/llvm-cvtres.cpp
===================================================================
--- llvm/trunk/tools/llvm-cvtres/llvm-cvtres.cpp
+++ llvm/trunk/tools/llvm-cvtres/llvm-cvtres.cpp
@@ -88,6 +88,13 @@
                   [&](const ErrorInfoBase &EI) { reportError(EI.message()); });
 }
 
+static uint32_t getTime() {
+  std::time_t Now = time(nullptr);
+  if (Now < 0 || !isUInt<32>(Now))
+    return UINT32_MAX;
+  return static_cast<uint32_t>(Now);
+}
+
 template <typename T> T error(Expected<T> EC) {
   if (!EC)
     error(EC.takeError());
@@ -142,6 +149,16 @@
     sys::path::replace_extension(OutputFile, ".obj");
   }
 
+  uint32_t DateTimeStamp;
+  if (llvm::opt::Arg *Arg = InputArgs.getLastArg(OPT_TIMESTAMP)) {
+    StringRef Value(Arg->getValue());
+    if (Value.getAsInteger(0, DateTimeStamp))
+      reportError(Twine("invalid timestamp: ") + Value +
+            ".  Expected 32-bit integer\n");
+  } else {
+    DateTimeStamp = getTime();
+  }
+
   if (Verbose) {
     outs() << "Machine: ";
     switch (MachineType) {
@@ -194,7 +211,8 @@
   }
 
   std::unique_ptr<MemoryBuffer> OutputBuffer =
-      error(llvm::object::writeWindowsResourceCOFF(MachineType, Parser));
+      error(llvm::object::writeWindowsResourceCOFF(MachineType, Parser,
+                                                   DateTimeStamp));
   auto FileOrErr =
       FileOutputBuffer::create(OutputFile, OutputBuffer->getBufferSize());
   if (!FileOrErr)