diff --git a/paths/qoc_participating-practices.yaml b/paths/qoc_participating-practices.yaml
index 14be5e9..0a7690c 100644
--- a/paths/qoc_participating-practices.yaml
+++ b/paths/qoc_participating-practices.yaml
@@ -40,9 +40,7 @@ get:
               calculatedAt:
                 description: |-
                   *OPTIONAL*. The timestamp when the group average was calculated. If not present, no group average calculation is available.
-                type: string
-                format: dateTime
-                example: 2023-04-01T12:30:00.000Z
+                $ref: ../schemas/dateTime.yaml
               refDate:
                 description: 'Groups reported are available for this date (dutch: _peildatum_).'
                 $ref: ../schemas/date.yaml
@@ -80,16 +78,12 @@ get:
                       description: |-
                         If present, this GP practice is calculated for this refDate for this care program, and the calculation
                         is based on a snapshot of GPIS data at this instant.
-                      type: string
-                      format: datetime
-                      example: 2023-04-01T12:30:00.000Z
+                      $ref: ../schemas/dateTime.yaml
                     mostRecentDataAvailable:
                       description: |-
                         If present, this GP practice's most recent available data is a GPIS snapshot with GPIS data at this instant.
                         Usually equal to `calculationBasedOn`, but can be newer. If not present, this GP practice has no data available.
-                      type: string
-                      format: datetime
-                      example: 2023-04-01T12:30:00.000Z
+                      $ref: ../schemas/dateTime.yaml
                   required:
                     - agb
                     - name
diff --git a/schemas/GPIS.yaml b/schemas/GPIS.yaml
index 877abb3..eabe7b3 100644
--- a/schemas/GPIS.yaml
+++ b/schemas/GPIS.yaml
@@ -1,4 +1,4 @@
-description: The source of the medical data used to produce this report (which General Practitioner Information System used, and when the data was provided).
+description: "The source of the medical data used to produce this report: which general practitioner information system was used, and when the data was provided."
 type: object
 properties:
   gpisType:
@@ -9,6 +9,4 @@ properties:
     description: |-
       The report is based on dossier data as it was on this timestamp; due to inaccuracies by GP information systems that source the data,
       this value is not always accurate and can be off by as much as a week.
-    type: string
-    format: dateTime
-    example: 2023-04-01T12:30:00.000Z
+    $ref: dateTime.yaml
diff --git a/schemas/date.yaml b/schemas/date.yaml
index 5c12ce5..a1bda14 100644
--- a/schemas/date.yaml
+++ b/schemas/date.yaml
@@ -1,5 +1,4 @@
-description: |-
-  Date without time part in ISO-8601 format. 
+description: Date without time part in ISO-8601 complete extended format.
 type: string
 format: date
 example: "1970-01-13"
diff --git a/schemas/dateTime.yaml b/schemas/dateTime.yaml
index 937552b..0a06b1e 100644
--- a/schemas/dateTime.yaml
+++ b/schemas/dateTime.yaml
@@ -1,4 +1,4 @@
-description: Date with time part in ISO-8601 format.
+description: Timestamp in complete basic representation of date and time according ISO 8601.
 type: string
 format: datetime
-example: "1970-01-13T13:59:00.123456"
+example: "19700131T235901"