diff --git a/src/dxtbx/format/FormatCBFMini.py b/src/dxtbx/format/FormatCBFMini.py
index 4561665fd..39060f84a 100644
--- a/src/dxtbx/format/FormatCBFMini.py
+++ b/src/dxtbx/format/FormatCBFMini.py
@@ -8,6 +8,7 @@
 from __future__ import annotations
 
 import binascii
+import datetime
 import os
 import pathlib
 import sys
@@ -73,6 +74,20 @@ def __init__(self, image_file, **kwargs):
         self._raw_data = None
         super().__init__(image_file, **kwargs)
 
+    @staticmethod
+    def _get_timestamp_from_raw_header(
+        header: str | list[str],
+    ) -> datetime.datetime | None:
+        """Given a raw header, or lines from, attempt to extract the timestamp field"""
+        if isinstance(header, str):
+            header = header.splitlines()
+        timestamp = None
+        for record in header:
+            if len(record[1:].split()) <= 2 and record.count(":") == 2:
+                timestamp = datetime.datetime.fromisoformat(record[1:].strip())
+                break
+        return timestamp
+
     def _start(self):
         """Open the image file, read the image header, copy it into a
         dictionary for future reference."""
diff --git a/src/dxtbx/format/FormatCBFMiniEigerPetraP13.py b/src/dxtbx/format/FormatCBFMiniEigerPetraP13.py
deleted file mode 100644
index d385435a0..000000000
--- a/src/dxtbx/format/FormatCBFMiniEigerPetraP13.py
+++ /dev/null
@@ -1,38 +0,0 @@
-"""An implementation of the CBF image reader for Eiger images"""
-
-
-from __future__ import annotations
-
-import sys
-
-from dxtbx.format.FormatCBFMiniEiger import FormatCBFMiniEiger
-
-
-class FormatCBFMiniEigerPetraP13(FormatCBFMiniEiger):
-    """A class for reading mini CBF format Eiger images, and correctly
-    constructing a model for the experiment from this. This tuned for Petra P13"""
-
-    @staticmethod
-    def understand(image_file):
-        """Check to see if this looks like an Eiger mini CBF format image,
-        i.e. we can make sense of it."""
-
-        header = FormatCBFMiniEiger.get_cbf_header(image_file)
-
-        for record in header.split("\n"):
-            if (
-                "# detector" in record.lower()
-                and "eiger" in record.lower()
-                and "E-32-0107" in record
-            ):
-                return True
-
-        return False
-
-    def _goniometer(self):
-        return self._goniometer_factory.known_axis((1, 0, 0))
-
-
-if __name__ == "__main__":
-    for arg in sys.argv[1:]:
-        print(FormatCBFMiniEigerPetraP13.understand(arg))
diff --git a/src/dxtbx/format/FormatCBFMiniEigerPetraP14.py b/src/dxtbx/format/FormatCBFMiniEigerPetraP14.py
index 15de04c1d..36b5cce91 100644
--- a/src/dxtbx/format/FormatCBFMiniEigerPetraP14.py
+++ b/src/dxtbx/format/FormatCBFMiniEigerPetraP14.py
@@ -3,6 +3,7 @@
 
 from __future__ import annotations
 
+import datetime
 import sys
 
 from dxtbx.format.FormatCBFMiniEiger import FormatCBFMiniEiger
@@ -19,11 +20,21 @@ def understand(image_file):
 
         header = FormatCBFMiniEiger.get_cbf_header(image_file)
 
+        # Valid from 22nd May 2021
+        expected_serial = "E-32-0129"
+        if timestamp := FormatCBFMiniEiger._get_timestamp_from_raw_header(header):
+            # We have a timestamp. Let's see what detector we should expect
+
+            # Before 22nd May 2021
+            if timestamp < datetime.datetime(2021, 5, 22):
+                expected_serial = "E-32-0107"
+
+        # Find the line recording detector serial, and check
         for record in header.split("\n"):
             if (
                 "# detector" in record.lower()
                 and "eiger" in record.lower()
-                and "E-32-0129" in record
+                and expected_serial in record
             ):
                 return True