diff --git a/Lib/importlib/_bootstrap.py b/Lib/importlib/_bootstrap.py
index 5b91c05..a87d178 100644
--- Lib/importlib/_bootstrap.py
+++ Lib/importlib/_bootstrap.py
@@ -666,8 +666,15 @@ def _compile_bytecode(data, name=None, bytecode_path=None, source_path=None):
 def _code_to_bytecode(code, mtime=0, source_size=0):
     """Compile a code object into bytecode for writing out to a byte-compiled
     file."""
+    """os and locale are required for the SOURCE_DATE_EPOCH
+    deterministic timestamp conditional."""
+    import os
+    import locale
     data = bytearray(MAGIC_NUMBER)
-    data.extend(_w_long(mtime))
+    if os.getenv('SOURCE_DATE_EPOCH'):
+        data.extend(_w_long(locale.atoi(os.getenv('SOURCE_DATE_EPOCH'))))
+    else:
+        data.extend(_w_long(mtime))
     data.extend(_w_long(source_size))
     data.extend(marshal.dumps(code))
     return data