fix: Update datetime definition/regex to match specification

src/schema/objects/formats.yaml

@@ -70,9 +70,18 @@ datetime:
   display_name: Datetime
   description: |
     A datetime in the form `"YYYY-MM-DDThh:mm:ss[.000000][Z]"`,
-    where [.000000] is an optional subsecond resolution between 1 and 6 decimal points,
-    and [Z] is an optional, valid timezone code.
-  pattern: '[0-9]{4}-[0-9]{2}-[0-9]{2}T(?:2[0-3]|[01][0-9]):[0-5][0-9]:[0-5][0-9](\.[0-9]{1,6})?([A-Z]{2,4})?'
+    where `[.000000]` is an optional subsecond resolution between 1 and 6 decimal points,
+    and `[Z]` is an optional literal character `Z` that indicates
+    Coordinated Universal Time (UTC).
+  pattern: "\
+    [0-9]{4}\
+    -(?:0[1-9]|1[0-2])\
+    -(?:0[1-9]|[12][0-9]|3[01])\
+    T(?:2[0-3]|[01][0-9])\
+    :[0-5][0-9]\
+    :(?:[0-5][0-9]|60)\
+    (?:\\.[0-9]{1,6})?\
+    Z?"
 file_relative:
   display_name: Path relative to the parent file
   description: |