diff --git a/pyproject.toml b/pyproject.toml
index 4fe21e6..36a685e 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -73,3 +73,5 @@ ignore = []
 "quantities/units/*.py" = ["F401"]
 "quantities/constants/*.py" = ["F401"]
 "quantities/__init__.py" = ["F401", "F403"]
+# Generated from NIST_codata.txt with one constant per line.
+"quantities/constants/_codata.py" = ["E501"]
diff --git a/quantities/constants/NIST_codata.txt b/quantities/constants/NIST_codata.txt
index 9f8094d..9881463 100644
--- a/quantities/constants/NIST_codata.txt
+++ b/quantities/constants/NIST_codata.txt
@@ -1,6 +1,6 @@
 
              Fundamental Physical Constants --- Complete Listing
-
+             2006 CODATA adjustment
 
   From:  http://physics.nist.gov/constants
 
diff --git a/quantities/constants/_codata.py b/quantities/constants/_codata.py
index 8cace73..310e81f 100644
--- a/quantities/constants/_codata.py
+++ b/quantities/constants/_codata.py
@@ -1,5 +1,6 @@
 # THIS FILE IS AUTOMATICALLY GENERATED
 # ANY CHANGES MADE HERE WILL BE LOST
+# Source: CODATA 2006 recommended values, from NIST_codata.txt
 
 physical_constants = {}
 
diff --git a/setup.py b/setup.py
index 1d139de..6da26f5 100755
--- a/setup.py
+++ b/setup.py
@@ -1,7 +1,8 @@
+import re
+
 from setuptools import Command, setup
 from setuptools.command.build_py import build_py as _build
 from setuptools.command.sdist import sdist as _sdist
-from datetime import datetime
 
 
 class data(Command):
@@ -19,12 +20,15 @@ def finalize_options(self):
     def run(self):
         with open('quantities/constants/NIST_codata.txt') as f:
             data = f.read()
+        edition = re.search(r'(\d{4}) CODATA adjustment', data)
+        if edition is None:
+            raise ValueError('CODATA edition not found in NIST_codata.txt')
         data = data.split('\n')[10:-1]
 
         with open('quantities/constants/_codata.py', 'w') as f:
             f.write('# THIS FILE IS AUTOMATICALLY GENERATED\n')
             f.write('# ANY CHANGES MADE HERE WILL BE LOST\n')
-            f.write(f'# LAST GENERATED: {datetime.now()}\n\n')
+            f.write(f'# Source: CODATA {edition[1]} recommended values, from NIST_codata.txt\n\n')
             f.write('physical_constants = {}\n\n')
             for line in data:
                 name = line[:55].rstrip().replace('mag.','magnetic')