diff --git a/cumulus/common.py b/cumulus/common.py
index 0cc43cf0..75e0024f 100644
--- a/cumulus/common.py
+++ b/cumulus/common.py
@@ -241,15 +241,23 @@ def print_header(name: str) -> None:
 #
 ###############################################################################
 
-def timestamp_datetime() -> str:
+def datetime_now() -> datetime.datetime:
+    """
+    UTC date and time, suitable for use as a FHIR 'instant' data type
+    """
+    return datetime.datetime.now(datetime.timezone.utc)
+
+
+def timestamp_datetime(time: datetime.datetime = None) -> str:
     """
     Human-readable UTC date and time
     :return: MMMM-DD-YYY hh:mm:ss
     """
-    return datetime.datetime.now(datetime.timezone.utc).strftime('%Y-%m-%d %H:%M:%S')
+    time = time or datetime_now()
+    return time.strftime('%Y-%m-%d %H:%M:%S')
 
 
-def timestamp_filename() -> str:
+def timestamp_filename(time: datetime.datetime = None) -> str:
     """
     Human-readable UTC date and time suitable for a filesystem path
 
@@ -257,4 +265,5 @@ def timestamp_filename() -> str:
 
     :return: MMMM-DD-YYY__hh.mm.ss
     """
-    return datetime.datetime.now(datetime.timezone.utc).strftime('%Y-%m-%d__%H.%M.%S')
+    time = time or datetime_now()
+    return time.strftime('%Y-%m-%d__%H.%M.%S')
diff --git a/cumulus/config.py b/cumulus/config.py
index 0f18af5f..a81e4c80 100644
--- a/cumulus/config.py
+++ b/cumulus/config.py
@@ -1,5 +1,6 @@
 """ETL job config with summary"""
 
+import datetime
 import os
 from socket import gethostname
 
@@ -15,6 +16,7 @@ def __init__(
             dir_input: str,
             store_format: store.Format,
             dir_phi: store.Root,
+            timestamp: datetime.datetime = None,
             comment: str = None,
             batch_size: int = 1,  # this default is never really used - overridden by command line args
     ):
@@ -28,7 +30,7 @@ def __init__(
         self.dir_input = dir_input
         self.format = store_format
         self.dir_phi = dir_phi
-        self.timestamp = common.timestamp_filename()
+        self.timestamp = common.timestamp_filename(timestamp)
         self.hostname = gethostname()
         self.comment = comment or ''
         self.batch_size = batch_size
diff --git a/cumulus/context.py b/cumulus/context.py
new file mode 100644
index 00000000..0b3445e4
--- /dev/null
+++ b/cumulus/context.py
@@ -0,0 +1,71 @@
+"""
+ETL job context, holding some persistent state between runs.
+"""
+
+import datetime
+from typing import Optional
+
+from cumulus import common
+
+
+class JobContext:
+    """
+    Context for an ETL job.
+
+    This is not really settings or config in the sense of user-derived values.
+    A prime example is "last successful run time" which the next run might want to use as part of its work
+    (like to only extract the changed data since the last run) but is otherwise ephemeral information.
+
+    Another possible (but not yet implemented) use might be to store some past config values,
+    like the last used output format. To either give the user a chance to correct a mistake or to know
+    how to change from one format to another.
+
+    This is stored in the phi/build directory and is thus safe to store possible PHI.
+    """
+
+    _LAST_SUCCESSFUL_DATETIME = 'last_successful_datetime'
+    _LAST_SUCCESSFUL_INPUT_DIR = 'last_successful_input_dir'
+    _LAST_SUCCESSFUL_OUTPUT_DIR = 'last_successful_output_dir'
+
+    def __init__(self, path: str):
+        """
+        :param path: path to context file
+        """
+        self._path: str = path
+        try:
+            self._data = common.read_json(path)
+        except (FileNotFoundError, PermissionError):
+            self._data = {}
+
+    @property
+    def last_successful_datetime(self) -> Optional[datetime.datetime]:
+        value = self._data.get(self._LAST_SUCCESSFUL_DATETIME)
+        if value is not None:
+            return datetime.datetime.fromisoformat(value)
+        return None
+
+    @last_successful_datetime.setter
+    def last_successful_datetime(self, value: datetime.datetime) -> None:
+        self._data[self._LAST_SUCCESSFUL_DATETIME] = value.isoformat()
+
+    @property
+    def last_successful_input_dir(self) -> Optional[str]:
+        return self._data.get(self._LAST_SUCCESSFUL_INPUT_DIR)
+
+    @last_successful_input_dir.setter
+    def last_successful_input_dir(self, value: str) -> None:
+        self._data[self._LAST_SUCCESSFUL_INPUT_DIR] = value
+
+    @property
+    def last_successful_output_dir(self) -> Optional[str]:
+        return self._data.get(self._LAST_SUCCESSFUL_OUTPUT_DIR)
+
+    @last_successful_output_dir.setter
+    def last_successful_output_dir(self, value: str) -> None:
+        self._data[self._LAST_SUCCESSFUL_OUTPUT_DIR] = value
+
+    def save(self) -> None:
+        common.write_json(self._path, self.as_json(), indent=4)  # pretty-print this since it isn't large
+
+    def as_json(self) -> dict:
+        return dict(self._data)
diff --git a/cumulus/etl.py b/cumulus/etl.py
index 29bca3d1..01c82d9e 100644
--- a/cumulus/etl.py
+++ b/cumulus/etl.py
@@ -24,7 +24,7 @@
 from fhirclient.models.patient import Patient
 from fhirclient.models.resource import Resource
 
-from cumulus import common, ctakes, deid, formats, loaders, store
+from cumulus import common, context, ctakes, deid, formats, loaders, store
 from cumulus.config import JobConfig, JobSummary
 
 ###############################################################################
@@ -361,6 +361,9 @@ def main(args: List[str]):
     root_output = store.Root(args.dir_output, create=True)
     root_phi = store.Root(args.dir_phi, create=True)
 
+    job_context = context.JobContext(root_phi.joinpath('context.json'))
+    job_datetime = common.datetime_now()  # grab timestamp before we do anything
+
     if args.input_format == 'i2b2':
         config_loader = loaders.I2b2Loader(root_input)
     else:
@@ -375,19 +378,27 @@ def main(args: List[str]):
 
     deid_dir = load_and_deidentify(config_loader)
 
+    # Prepare config for jobs
     config = JobConfig(config_loader, deid_dir.name, config_store, root_phi, comment=args.comment,
-                       batch_size=args.batch_size)
-
+                       batch_size=args.batch_size, timestamp=job_datetime)
+    common.write_json(config.path_config(), config.as_json(), indent=4)
     common.print_header('Configuration:')
     print(json.dumps(config.as_json(), indent=4))
 
-    common.write_json(config.path_config(), config.as_json(), indent=4)
-
+    # Finally, actually run the meat of the pipeline!
     summaries = etl_job(config)
+
+    # Print results to the console
     common.print_header('Results:')
     for summary in summaries:
         print(json.dumps(summary.as_json(), indent=4))
 
+    # Update job context for future runs
+    job_context.last_successful_datetime = job_datetime
+    job_context.last_successful_input_dir = root_input.path
+    job_context.last_successful_output_dir = root_output.path
+    job_context.save()
+
 
 def main_cli():
     main(sys.argv[1:])
diff --git a/tests/test_context.py b/tests/test_context.py
new file mode 100644
index 00000000..4928bba3
--- /dev/null
+++ b/tests/test_context.py
@@ -0,0 +1,49 @@
+"""Tests for context.py"""
+
+import datetime
+import json
+import tempfile
+import unittest
+
+from cumulus.context import JobContext
+
+
+class TestJobContext(unittest.TestCase):
+    """Test case for JobContext"""
+
+    def test_missing_file_context(self):
+        context = JobContext('nope')
+        self.assertEqual({}, context.as_json())
+
+    def test_save_and_load(self):
+        with tempfile.NamedTemporaryFile(mode='w+') as f:
+            json.dump({
+                'last_successful_input_dir': '/input/dir',
+            }, f)
+            f.flush()
+
+            context = JobContext(f.name)
+            self.assertEqual({
+                'last_successful_input_dir': '/input/dir',
+            }, context.as_json())
+
+            context.last_successful_datetime = datetime.datetime(2008, 5, 1, 14, 30, 30, tzinfo=datetime.timezone.utc)
+            self.assertEqual({
+                'last_successful_datetime': '2008-05-01T14:30:30+00:00',
+                'last_successful_input_dir': '/input/dir',
+            }, context.as_json())
+
+            context.save()
+            context2 = JobContext(f.name)
+            self.assertEqual(context.as_json(), context2.as_json())
+
+    def test_last_successful_props(self):
+        context = JobContext('nope')
+        context.last_successful_datetime = datetime.datetime(2008, 5, 1, 14, 30, 30, tzinfo=datetime.timezone.utc)
+        context.last_successful_input_dir = '/input'
+        context.last_successful_output_dir = '/output'
+        self.assertEqual({
+            'last_successful_datetime': '2008-05-01T14:30:30+00:00',
+            'last_successful_input_dir': '/input',
+            'last_successful_output_dir': '/output',
+        }, context.as_json())
diff --git a/tests/test_etl.py b/tests/test_etl.py
index 01a20075..f65d6ade 100644
--- a/tests/test_etl.py
+++ b/tests/test_etl.py
@@ -16,7 +16,7 @@
 import s3fs
 from fhirclient.models.extension import Extension
 
-from cumulus import common, config, deid, etl, store
+from cumulus import common, config, context, deid, etl, store
 from cumulus.loaders.i2b2 import extract
 
 from tests.ctakesmock import CtakesMixin, fake_ctakes_extract
@@ -191,6 +191,38 @@ def test_comment(self):
         self.assertEqual(config_file['comment'], 'Run by foo on machine bar')
 
 
+class TestI2b2EtlJobContext(BaseI2b2EtlSimple):
+    """Test case for the job context data"""
+
+    def setUp(self):
+        super().setUp()
+        self.context_path = os.path.join(self.phi_path, 'context.json')
+
+    def test_context_updated_on_success(self):
+        """Verify that we update the success timestamp etc. when the job succeeds"""
+        self.run_etl()
+        job_context = context.JobContext(self.context_path)
+        self.assertEqual('2021-09-14T21:23:45+00:00', job_context.last_successful_datetime.isoformat())
+        self.assertEqual(self.input_path, job_context.last_successful_input_dir)
+        self.assertEqual(self.output_path, job_context.last_successful_output_dir)
+
+    def test_context_not_updated_on_failure(self):
+        """Verify that we don't update the success timestamp etc. when the job fails"""
+        input_context = {
+            'last_successful_datetime': '2000-01-01T10:10:10+00:00',
+            'last_successful_input': '/input',
+            'last_successful_output': '/output',
+        }
+        common.write_json(self.context_path, input_context)
+
+        with mock.patch('cumulus.etl.etl_job', side_effect=ZeroDivisionError):
+            with self.assertRaises(ZeroDivisionError):
+                self.run_etl()
+
+        # Confirm we didn't change anything
+        self.assertEqual(input_context, common.read_json(self.context_path))
+
+
 class TestI2b2EtlBatches(BaseI2b2EtlSimple):
     """Test case for etl batching"""