diff --git a/CHANGELOG.md b/CHANGELOG.md
index 108379f..ad590ba 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,17 @@
 # Change log
 
+## Release 0.6.x (2023-08-dd)
+
+New features:
+
+- Support for two environment variables was added. Both changes enable achieving consistent version/tag info in the gh-based vocabulary management (related [voc4cat-template #11](https://github.com/nfdi4cat/voc4cat-template/issues/11)). #148
+  - `VOC4CAT_MODIFIED` - If set to a truthy value, the current date is used as modified date; the date in the source is ignored.
+  - `VOC4CAT_VERSION` - version string; if present this version info has highest precedence. A leading "v" will be removed.
+
+Bug fixes:
+
+- Modified date of concept scheme was not transferred from xlsx to rdf. #147, #148
+
 ## Release 0.6.2 (2023-08-10)
 
 New features:
diff --git a/src/voc4cat/docs.py b/src/voc4cat/docs.py
index 2f94da2..bf39c08 100644
--- a/src/voc4cat/docs.py
+++ b/src/voc4cat/docs.py
@@ -32,6 +32,14 @@ def run_pylode(turtle_file: Path, output_path: Path) -> None:
         '<section id="overview">',
         '<section id="overview" style="display: none;">',
     )
+    content = content.replace(
+        "<dt>Ontology RDF</dt>",
+        "<dt>Vocabulary RDF</dt>",
+    )
+    content = content.replace(
+        f'<dd><a href="{filename.stem}.ttl">RDF (turtle)</a></dd>',
+        f'<dd><a href="../{filename.stem}.ttl">RDF (turtle)</a></dd>',
+    )
     with open(outfile, "w") as html_file:
         html_file.write(content)
 
diff --git a/src/voc4cat/models.py b/src/voc4cat/models.py
index 44dab3c..e907251 100644
--- a/src/voc4cat/models.py
+++ b/src/voc4cat/models.py
@@ -1,5 +1,6 @@
 import datetime
 import logging
+import os
 from itertools import chain
 from typing import List, Union
 
@@ -169,6 +170,12 @@ def creator_must_be_from_list(cls, v):
             raise ValueError(msg)
         return v
 
+    @validator("modified")
+    def set_modified_date_if_missing(cls, v):
+        if os.getenv("CI") is not None:  # Don't track modified date in GitHub.
+            v = None
+        return v
+
     @validator("publisher")
     def publisher_must_be_from_list(cls, v):
         if v not in ORGANISATIONS:
@@ -176,6 +183,18 @@ def publisher_must_be_from_list(cls, v):
             raise ValueError(msg)
         return v
 
+    @validator("version")
+    def version_from_env(cls, v):
+        if os.getenv("CI") is not None:  # Don't track version in GitHub.
+            v = None
+        version_from_env = os.getenv("VOC4CAT_VERSION")
+        if version_from_env is not None:
+            if not version_from_env.startswith("v"):
+                msg = f'Invalid environment variable VOC4CAT_VERSION "{version_from_env}". Version must start with letter "v".'
+                raise ValueError(msg)
+            v = version_from_env
+        return v
+
     def to_graph(self):
         g = Graph()
         v = URIRef(self.uri)
@@ -187,25 +206,10 @@ def to_graph(self):
         g.add((v, SKOS.prefLabel, Literal(self.title, lang="en")))
         g.add((v, SKOS.definition, Literal(self.description, lang="en")))
         g.add((v, DCTERMS.created, Literal(self.created, datatype=XSD.date)))
-        if self.modified is not None:
-            g.add((v, DCTERMS.modified, Literal(self.created, datatype=XSD.date)))
-        else:
-            g.add(
-                (
-                    v,
-                    DCTERMS.modified,
-                    Literal(
-                        datetime.datetime.now(datetime.timezone.utc).strftime(
-                            "%Y-%m-%d"
-                        ),
-                        datatype=XSD.date,
-                    ),
-                )
-            )
+        g.add((v, DCTERMS.modified, Literal(self.modified, datatype=XSD.date))),
         g.add((v, DCTERMS.creator, ORGANISATIONS[self.creator]))
         g.add((v, DCTERMS.publisher, ORGANISATIONS[self.publisher]))
-        if self.version is not None:
-            g.add((v, OWL.versionInfo, Literal(self.version)))
+        g.add((v, OWL.versionInfo, Literal(self.version)))
         g.add((v, DCTERMS.provenance, Literal(self.provenance, lang="en")))
         if self.custodian is not None:
             g.add((v, DCAT.contactPoint, Literal(self.custodian)))
@@ -224,7 +228,7 @@ def to_excel(self, wb: Workbook):
         ws["B3"] = self.title
         ws["B4"] = self.description
         ws["B5"] = self.created.isoformat()
-        ws["B6"] = self.modified.isoformat()
+        ws["B6"] = None if self.modified is None else self.modified.isoformat()
         ws["B7"] = self.creator
         ws["B8"] = self.publisher
         ws["B9"] = self.version
diff --git a/src/voc4cat/transform.py b/src/voc4cat/transform.py
index 454e34a..ec131c6 100644
--- a/src/voc4cat/transform.py
+++ b/src/voc4cat/transform.py
@@ -1,4 +1,5 @@
 import logging
+import os
 import shutil
 from collections import defaultdict
 from itertools import count, zip_longest
@@ -7,8 +8,8 @@
 
 import openpyxl
 from openpyxl.styles import Alignment
-from rdflib import Graph
-from rdflib.namespace import SKOS
+from rdflib import Graph, Literal
+from rdflib.namespace import DCTERMS, OWL, RDF, SKOS, XSD
 
 from voc4cat import config
 from voc4cat.checks import Voc4catError
@@ -27,7 +28,7 @@
 def extract_numeric_id_from_iri(iri):
     iri_path = urlsplit(iri).path
     reverse_id = []
-    for char in reversed(iri_path):  # pragma: no cover
+    for char in reversed(iri_path):
         if char.isdigit():
             reverse_id.append(char)
         elif char == "/":
@@ -63,6 +64,27 @@ def write_split_turtle(vocab_graph: Graph, outdir: Path) -> None:
         logger.debug("-> wrote %i %ss-file(s).", len(qresults), skos_class)
 
 
+def autoversion_cs(graph: Graph) -> Graph:
+    """Set modified date and version if "requested" via environment variables."""
+    if any(graph.triples((None, RDF.type, SKOS.ConceptScheme))):
+        cs, _, _ = next(graph.triples((None, RDF.type, SKOS.ConceptScheme)))
+    if os.getenv("VOC4CAT_MODIFIED") is not None:
+        graph.remove((None, DCTERMS.modified, None))
+        date_modified = os.getenv("VOC4CAT_MODIFIED")
+        graph.add((cs, DCTERMS.modified, Literal(date_modified, datatype=XSD.date)))
+    if os.getenv("VOC4CAT_VERSION") is not None:
+        graph.remove((None, OWL.versionInfo, None))
+        version = os.getenv("VOC4CAT_VERSION")
+        if version is not None and not version.startswith("v"):
+            msg = 'Invalid environment variable VOC4CAT_VERSION "%s". Version must start with letter "v".'
+            logger.error(msg, version)
+            raise Voc4catError(msg % version)
+        graph.add(
+            (cs, OWL.versionInfo, Literal(version)),
+        )
+    return graph
+
+
 def join_split_turtle(vocab_dir: Path) -> Graph:
     # Search recursively all turtle files belonging to the concept scheme
     turtle_files = vocab_dir.rglob("*.ttl")
@@ -71,6 +93,11 @@ def join_split_turtle(vocab_dir: Path) -> Graph:
     # Load each turtle file into a separate graph and merge it into the concept scheme graph
     for file in turtle_files:
         graph = Graph().parse(file, format="turtle")
+        # Set modified date if "requested" via environment variable.
+        if file.name == "concept_scheme.ttl" or any(
+            graph.triples((None, RDF.type, SKOS.ConceptScheme))
+        ):
+            graph = autoversion_cs(graph)
         cs_graph += graph
     cs_graph.serialize(destination=vocab_dir.with_suffix(".ttl"), format="turtle")
     return cs_graph
diff --git a/tests/templ_versions/043_exhaustive_example.xlsx b/tests/templ_versions/043_exhaustive_example.xlsx
index 17a6fd4..a23968b 100644
Binary files a/tests/templ_versions/043_exhaustive_example.xlsx and b/tests/templ_versions/043_exhaustive_example.xlsx differ
diff --git a/tests/templ_versions/043_exhaustive_example_perfect_output.ttl b/tests/templ_versions/043_exhaustive_example_perfect_output.ttl
index e033013..0349cf9 100644
--- a/tests/templ_versions/043_exhaustive_example_perfect_output.ttl
+++ b/tests/templ_versions/043_exhaustive_example_perfect_output.ttl
@@ -27,7 +27,7 @@ cs: a skos:ConceptScheme ;
     dcterms:created "2022-03-07"^^xsd:date ;
     dcterms:creator <https://linked.data.gov.au/org/cgi> ;
     dcterms:hasPart <http://example.org/example_collection_uri> ;
-    dcterms:modified "2022-03-07"^^xsd:date ;
+    dcterms:modified "2022-03-10"^^xsd:date ;
     dcterms:provenance "Example Provenance"@en ;
     dcterms:publisher <https://linked.data.gov.au/org/cgi> ;
     rdfs:seeAlso "1.2.3.4" ;
diff --git a/tests/test_models.py b/tests/test_models.py
index 3d304cb..d79eb3d 100644
--- a/tests/test_models.py
+++ b/tests/test_models.py
@@ -1,3 +1,7 @@
+import datetime
+import os
+from unittest import mock
+
 import pytest
 from pydantic.error_wrappers import ValidationError
 from rdflib import Graph
@@ -81,20 +85,81 @@ def test_check_uri_vs_config(datadir, temp_config):
 # === From here on: "old" tests from rdflib.vocexcel ===
 
 
+@mock.patch.dict(os.environ, clear=True)  # required to hide gh-action environment vars
 def test_vocabulary_valid():
-    ConceptScheme(
+    cs = ConceptScheme(
+        uri="https://linked.data.gov.au/def/borehole-start-point",
+        title="Borehole Start Point",
+        description="Indicates the nature of the borehole start point location",
+        created="2020-04-02",
+        modified="2020-04-04",
+        creator="GSQ",
+        publisher="GSQ",
+        version="1.0",
+        provenance="Derived from the 2011-09 version of CGI Borehole start point list",
+        custodian="Vance Kelly",
+        pid="http://pid.geoscience.gov.au/dataset/ga/114541",
+    )
+    assert cs.modified == datetime.date(2020, 4, 4)
+    assert cs.version == "1.0"
+
+
+@mock.patch.dict(os.environ, {"CI": ""})
+def test_vocabulary_valid_in_ci():
+    cs = ConceptScheme(
+        uri="https://linked.data.gov.au/def/borehole-start-point",
+        title="Borehole Start Point",
+        description="Indicates the nature of the borehole start point location",
+        created="2020-04-02",
+        modified="2020-04-04",
+        creator="GSQ",
+        publisher="GSQ",
+        version="1.0",
+        provenance="Derived from the 2011-09 version of CGI Borehole start point list",
+        custodian="Vance Kelly",
+        pid="http://pid.geoscience.gov.au/dataset/ga/114541",
+    )
+    assert cs.modified is None
+    assert cs.version is None
+
+
+@mock.patch.dict(os.environ, {"CI": "", "VOC4CAT_VERSION": "v2023-08-15"})
+def test_vocabulary_valid_version_via_envvar():
+    cs = ConceptScheme(
         uri="https://linked.data.gov.au/def/borehole-start-point",
         title="Borehole Start Point",
         description="Indicates the nature of the borehole start point location",
         created="2020-04-02",
-        modified="2020-04-02",
+        modified="2020-04-04",
         creator="GSQ",
         publisher="GSQ",
-        version="",
+        version="1.0",
         provenance="Derived from the 2011-09 version of CGI Borehole start point list",
         custodian="Vance Kelly",
         pid="http://pid.geoscience.gov.au/dataset/ga/114541",
     )
+    assert cs.modified is None
+    assert cs.version == "v2023-08-15"
+
+
+@mock.patch.dict(os.environ, {"CI": "", "VOC4CAT_VERSION": "2023-08-15"})
+def test_vocabulary_invalid_version_via_envvar():
+    with pytest.raises(
+        ValidationError, match="Invalid environment variable VOC4CAT_VERSION"
+    ):
+        ConceptScheme(
+            uri="https://linked.data.gov.au/def/borehole-start-point",
+            title="Borehole Start Point",
+            description="Indicates the nature of the borehole start point location",
+            created="2020-04-02",
+            modified="2020-04-04",
+            creator="GSQ",
+            publisher="GSQ",
+            version="1.0",
+            provenance="Derived from the 2011-09 version of CGI Borehole start point list",
+            custodian="Vance Kelly",
+            pid="http://pid.geoscience.gov.au/dataset/ga/114541",
+        )
 
 
 def test_vocabulary_invalid_uri():
@@ -104,7 +169,7 @@ def test_vocabulary_invalid_uri():
             title="Borehole Start Point",
             description="Indicates the nature of the borehole start point location",
             created="2020-04-02",
-            modified="02/042020",
+            modified=None,
             creator="GSQ",
             publisher="GSQ",
             version="",
@@ -121,7 +186,7 @@ def test_vocabulary_invalid_created_date():
             title="Borehole Start Point",
             description="Indicates the nature of the borehole start point location",
             created="2020-04",
-            modified="2020-04-02",
+            modified="2020-04-04",
             creator="GSQ",
             publisher="GSQ",
             version="",
@@ -138,7 +203,7 @@ def test_vocabulary_invalid_publisher():
             title="Borehole Start Point",
             description="Indicates the nature of the borehole start point location",
             created="2020-04-02",
-            modified="2020-04-02",
+            modified="2020-04-04",
             creator="GSQ",
             publisher="WHO",
             version="",
diff --git a/tests/test_template043.py b/tests/test_template043.py
index 8de5bb2..beebabc 100644
--- a/tests/test_template043.py
+++ b/tests/test_template043.py
@@ -1,4 +1,6 @@
+import os
 from pathlib import Path
+from unittest import mock
 
 import pytest
 import voc4cat
@@ -39,6 +41,7 @@ def test_simple():
     ) in g, "Provenance for vocab is not correct"
 
 
+@mock.patch.dict(os.environ, clear=True)  # required to hide gh-action environment vars
 def test_exhaustive_template_is_isomorphic():
     g1 = Graph().parse(
         Path(__file__).parent
@@ -52,6 +55,7 @@ def test_exhaustive_template_is_isomorphic():
     assert compare.isomorphic(g1, g2), "Graphs are not Isomorphic"
 
 
+@mock.patch.dict(os.environ, clear=True)  # required to hide gh-action environment vars
 def test_rdf_to_excel():
     g1 = Graph().parse(
         Path(__file__).parent
diff --git a/tests/test_transform.py b/tests/test_transform.py
index 5b0daa0..064d6d0 100644
--- a/tests/test_transform.py
+++ b/tests/test_transform.py
@@ -1,8 +1,12 @@
 import logging
+import os
 import shutil
+from unittest import mock
 
 import pytest
 from openpyxl import load_workbook
+from rdflib import Graph, Literal
+from rdflib.namespace import DCTERMS, OWL, SKOS, XSD
 from test_cli import (
     CS_CYCLES,
     CS_CYCLES_INDENT_DOT,
@@ -600,3 +604,69 @@ def test_join(monkeypatch, datadir, tmp_path, opt, caplog):
     assert (vocdir.parent / CS_SIMPLE_TURTLE).exists()
     if opt:
         assert not vocdir.exists()
+
+
+@mock.patch.dict(
+    os.environ, {"CI": "", "VOC4CAT_VERSION": "v2.0", "VOC4CAT_MODIFIED": "2023-08-15"}
+)
+def test_join_with_envvars(monkeypatch, datadir, tmp_path, caplog):
+    monkeypatch.chdir(tmp_path)
+    shutil.copy(datadir / CS_SIMPLE_TURTLE, tmp_path)
+    # create dir with split files
+    main_cli(["transform", "-v", "--split", "--inplace", str(tmp_path)])
+    # join files again as test
+    cmd = ["transform", "-v", "--join"]
+    cmd.append(str(tmp_path))
+    with caplog.at_level(logging.DEBUG):
+        main_cli(cmd)
+    assert "-> joined vocabulary into" in caplog.text
+    # Were version and modified date correctly set?
+    graph = Graph().parse(CS_SIMPLE_TURTLE, format="turtle")
+    cs_query = "SELECT ?iri WHERE {?iri a skos:ConceptScheme.}"
+    qresults = [*graph.query(cs_query, initNs={"skos": SKOS})]
+    assert len(qresults) == 1
+
+    cs_iri = qresults[0][0]
+    assert (
+        len(
+            [
+                *graph.triples(
+                    (cs_iri, OWL.versionInfo, Literal("v2.0")),
+                )
+            ]
+        )
+        == 1
+    )
+
+    assert (
+        len(
+            [
+                *graph.triples(
+                    (
+                        cs_iri,
+                        DCTERMS.modified,
+                        Literal("2023-08-15", datatype=XSD.date),
+                    ),
+                )
+            ]
+        )
+        == 1
+    )
+
+
+@mock.patch.dict(
+    os.environ, {"CI": "", "VOC4CAT_VERSION": "2.0", "VOC4CAT_MODIFIED": "2023-08-15"}
+)
+def test_join_with_invalid_envvar(monkeypatch, datadir, tmp_path, caplog):
+    monkeypatch.chdir(tmp_path)
+    shutil.copy(datadir / CS_SIMPLE_TURTLE, tmp_path)
+    # create dir with split files
+    main_cli(["transform", "-v", "--split", "--inplace", str(tmp_path)])
+    # join files again as test
+    cmd = ["transform", "-v", "--join"]
+    cmd.append(str(tmp_path))
+    with caplog.at_level(logging.ERROR), pytest.raises(
+        Voc4catError, match="Invalid environment variable VOC4CAT_VERSION"
+    ):
+        main_cli(cmd)
+    assert 'Invalid environment variable VOC4CAT_VERSION "2.0"' in caplog.text