Index: lib/Lex/PPMacroExpansion.cpp
===================================================================
--- lib/Lex/PPMacroExpansion.cpp
+++ lib/Lex/PPMacroExpansion.cpp
@@ -1013,7 +1013,12 @@
 /// the identifier tokens inserted.
 static void ComputeDATE_TIME(SourceLocation &DATELoc, SourceLocation &TIMELoc,
                              Preprocessor &PP) {
-  time_t TT = time(nullptr);
+  time_t TT;
+  const char *envValue = getenv("SOURCE_DATE_EPOCH");
+  if (envValue != nullptr)
+    TT = strtol(envValue, nullptr, 10);
+  else
+    TT = time(nullptr);
   struct tm *TM = localtime(&TT);
 
   static const char * const Months[] = {