--- a/docs/conf.py	Sat May 16 15:16:42 2026 +0200
+++ b/docs/conf.py	Sat May 16 22:28:55 2026 +0200
@@ -14,6 +14,7 @@
 import pygments.lexers
 import pygments.filters
 import sphinx.util.logging
+import sphinx.transforms
 
 sys.path.insert(0, os.path.dirname(os.path.abspath('.')))
 
@@ -108,15 +109,6 @@
 
 rst_prolog = """
 .. role:: algpseudocode(code)
-.. |release_date| replace:: %s
-.. |release_rev| replace:: %s
-""" % (release_date, release_rev)
-if define_rest_keywords:
-    rst_prolog += """\
-.. |VCSJustDate| replace:: %s
-.. |VCSRevision| replace:: %s
-""" % (release_date, release_rev)
-rst_epilog = """
 .. _Pygments: https://pygments.org/
 .. _Sphinx: https://www.sphinx-doc.org
 .. _Python: https://www.python.org/
@@ -175,6 +167,34 @@
 ]
 
 
+class IAMCustomSubstitutions(sphinx.transforms.SphinxTransform):
+
+    """Implement custom variable substitutions"""
+
+    default_priority = sphinx.transforms.DefaultSubstitutions.default_priority
+
+    _SUBSTITUTIONS = {
+        "release_date": release_date,
+        "release_rev": release_rev
+    }
+    if define_rest_keywords:
+        _SUBSTITUTIONS.update(
+            {"VCSJustDate": release_date,
+             "VCSRevision": release_rev,
+             "VCSHGRevision": release_rev})
+
+    def apply(self):
+        from docutils import nodes
+        for ref in self.document.traverse(nodes.substitution_reference):
+            refname = ref['refname']
+            if refname in self._SUBSTITUTIONS:
+                stext = self._SUBSTITUTIONS[refname]
+                ref.replace_self(nodes.Text(stext, stext))
+            #if refname in ('release_date' 'release_rev'):
+            #    stext = self.config[refname]
+            #    ref.replace_self(nodes.Text(stext, stext))
+
+
 def setup(app):
     #
     # Custom release_date and commit id variables with a custom substitution
@@ -182,6 +202,8 @@
     #
     app.add_config_value('release_date', '', 'env')
     app.add_config_value('release_rev', '', 'env')
+    # Custom variable substitution
+    app.add_transform(IAMCustomSubstitutions)
 
     #
     # Add a custom lexer: AlgPseudocodeLexer with custom init option "no_end"