diff --git a/README.md b/README.md
index 33f599f..f7e0041 100644
--- a/README.md
+++ b/README.md
@@ -77,6 +77,12 @@ Valijson has a notion of strong and weak typing. By default, strong typing is us
 Validator validator;
 ```
 
+This is equivalent to:
+
+```cpp
+Validator validator(Validator::kStrongTypes);
+```
+
 This validator will not attempt to cast between types to satisfy a schema. So the string `"23"` will not be parsed as a number.
 
 Alternatively, weak typing can be used:
@@ -87,6 +93,22 @@ Validator validator(Validator::kWeakTypes);
 
 This will create a validator that will attempt to cast values to satisfy a schema. The original motivation for this was to support the Boost Property Tree library, which can parse JSON, but stores values as strings.
 
+### Strict vs Permissive Date/Time Formats
+
+JSON Schema supports validation of certain types using the `format` keyword. Supported formats include `time`, `date`, and `date-time`. When `date-time` is used, the input is validated according to [RFC 3999](./doc/specifications/rfc3339-timestamps.txt). By default, RFC 3999 requires that all date/time strings are unambiguous - i.e. are defined in terms of a local time zone. This is controlled by the `Z` suffix (for UTC) or a `+01:00` style modifier.
+
+Valijson can be configured to allow ambiguous date/time strings.
+
+```cpp
+Validator validator(Validator::kStrongTypes, Validator::kPermissiveDateTime);
+```
+
+The default is strict date/time validation, which is equivalent to:
+
+```cpp
+Validator validator(Validator::kStrongTypes, Validator::kStrictDateTime);
+```
+
 ## Regular Expression Engine
 
 When enforcing a 'pattern' property, a regular expression engine is used. By default, the default regular expression (`DefaultRegexEngine`) uses `std::regex`.
diff --git a/include/valijson/validator.hpp b/include/valijson/validator.hpp
index 2f0df22..75b2646 100644
--- a/include/valijson/validator.hpp
+++ b/include/valijson/validator.hpp
@@ -35,7 +35,9 @@ class ValidatorT
      * @brief  Construct a Validator that uses strong type checking by default
      */
     ValidatorT()
-      : strictTypes(true) { }
+      : strictTypes(true)
+      , strictDateTime(true)
+    { }
 
     /**
      * @brief  Construct a Validator using a specific type checking mode