diff --git a/rama-http/src/headers/x_robots_tag/custom_rule.rs b/rama-http/src/headers/x_robots_tag/custom_rule.rs
index aeb86a27..bb2ab466 100644
--- a/rama-http/src/headers/x_robots_tag/custom_rule.rs
+++ b/rama-http/src/headers/x_robots_tag/custom_rule.rs
@@ -1,31 +1,31 @@
 use crate::headers::util::value_string::{FromStrError, HeaderValueString};
 
 #[derive(Clone, Debug, Eq, PartialEq)]
-pub struct CustomRule {
+pub(super) struct CustomRule {
     key: HeaderValueString,
     value: Option<HeaderValueString>,
 }
 
 impl CustomRule {
-    pub fn new(key: &str) -> Result<Self, FromStrError> {
+    pub(super) fn new(key: &str) -> Result<Self, FromStrError> {
         Ok(Self {
             key: key.parse()?,
             value: None,
         })
     }
 
-    pub fn with_value(key: &str, value: &str) -> Result<Self, FromStrError> {
+    pub(super) fn with_value(key: &str, value: &str) -> Result<Self, FromStrError> {
         Ok(Self {
             key: key.parse()?,
             value: Some(value.parse()?),
         })
     }
 
-    pub fn key(&self) -> &HeaderValueString {
+    pub(super) fn key(&self) -> &HeaderValueString {
         &self.key
     }
 
-    pub fn value(&self) -> Option<&HeaderValueString> {
+    pub(super) fn value(&self) -> Option<&HeaderValueString> {
         self.value.as_ref()
     }
 }
diff --git a/rama-http/src/headers/x_robots_tag/max_image_preview_setting.rs b/rama-http/src/headers/x_robots_tag/max_image_preview_setting.rs
index c5c5f2df..628c0233 100644
--- a/rama-http/src/headers/x_robots_tag/max_image_preview_setting.rs
+++ b/rama-http/src/headers/x_robots_tag/max_image_preview_setting.rs
@@ -3,7 +3,7 @@ use std::fmt::Formatter;
 use std::str::FromStr;
 
 #[derive(Clone, Debug, Eq, PartialEq)]
-pub enum MaxImagePreviewSetting {
+pub(super) enum MaxImagePreviewSetting {
     None,
     Standard,
     Large,
diff --git a/rama-http/src/headers/x_robots_tag/mod.rs b/rama-http/src/headers/x_robots_tag/mod.rs
index 8d5de836..a2a205e7 100644
--- a/rama-http/src/headers/x_robots_tag/mod.rs
+++ b/rama-http/src/headers/x_robots_tag/mod.rs
@@ -1,11 +1,8 @@
-pub mod robots_tag;
-pub use robots_tag::RobotsTag;
+mod robots_tag;
 
-pub mod robots_tag_builder;
-pub use robots_tag_builder::RobotsTagBuilder;
+mod robots_tag_builder;
 
-pub mod max_image_preview_setting;
-pub use max_image_preview_setting::MaxImagePreviewSetting;
+mod max_image_preview_setting;
 
-pub mod custom_rule;
-pub use custom_rule::CustomRule;
+mod custom_rule;
+mod valid_date;
diff --git a/rama-http/src/headers/x_robots_tag/robots_tag.rs b/rama-http/src/headers/x_robots_tag/robots_tag.rs
index 2eccd50b..02077166 100644
--- a/rama-http/src/headers/x_robots_tag/robots_tag.rs
+++ b/rama-http/src/headers/x_robots_tag/robots_tag.rs
@@ -2,15 +2,21 @@ use crate::headers::util::value_string::HeaderValueString;
 use crate::headers::x_robots_tag::custom_rule::CustomRule;
 use crate::headers::x_robots_tag::max_image_preview_setting::MaxImagePreviewSetting;
 use crate::headers::x_robots_tag::robots_tag_builder::RobotsTagBuilder;
+use crate::headers::x_robots_tag::valid_date::ValidDate;
 
 macro_rules! getter_setter {
     ($field:ident, $type:ty) => {
         paste::paste! {
-            pub fn [<$field>](&self) -> $type {
+            pub(super) fn [<$field>](&self) -> $type {
                 self.[<$field>]
             }
 
-            pub fn [<set_ $field>](&mut self, [<$field>]: $type) -> &mut Self {
+            pub(super) fn [<set_ $field>](&mut self, [<$field>]: $type) -> &mut Self {
+                self.[<$field>] = [<$field>];
+                self
+            }
+
+            pub(super) fn [<with_ $field>](mut self, [<$field>]: $type) -> Self {
                 self.[<$field>] = [<$field>];
                 self
             }
@@ -19,25 +25,17 @@ macro_rules! getter_setter {
 
     ($field:ident, $type:ty, optional) => {
         paste::paste! {
-            pub fn [<$field>](&self) -> Option<&$type> {
+            pub(super) fn [<$field>](&self) -> Option<&$type> {
                 self.[<$field>].as_ref()
             }
 
-            pub fn [<set_ $field>](&mut self, [<$field>]: $type) -> &mut Self {
+            pub(super) fn [<set_ $field>](&mut self, [<$field>]: $type) -> &mut Self {
                 self.[<$field>] = Some([<$field>]);
                 self
             }
-        }
-    };
-
-    ($field:ident, $type:ty, vec) => {
-        paste::paste! {
-            pub fn [<$field>](&self) -> &Vec<$type> {
-                &self.[<$field>]
-            }
 
-            pub fn [<add_ $field>](&mut self, [<$field>]: $type) -> &mut Self {
-                self.[<$field>].push([<$field>]);
+            pub(super) fn [<with_ $field>](mut self, [<$field>]: $type) -> Self {
+                self.[<$field>] = Some([<$field>]);
                 self
             }
         }
@@ -45,7 +43,7 @@ macro_rules! getter_setter {
 }
 
 #[derive(Clone, Debug, Eq, PartialEq, Default)]
-pub struct RobotsTag {
+pub(super) struct RobotsTag {
     bot_name: Option<HeaderValueString>,
     all: bool,
     no_index: bool,
@@ -58,7 +56,7 @@ pub struct RobotsTag {
     max_video_preview: Option<u32>,
     no_translate: bool,
     no_image_index: bool,
-    unavailable_after: Option<chrono::DateTime<chrono::Utc>>, // "A date must be specified in a format such as RFC 822, RFC 850, or ISO 8601."
+    unavailable_after: Option<ValidDate>, // "A date must be specified in a format such as RFC 822, RFC 850, or ISO 8601."
     // custom rules
     no_ai: bool,
     no_image_ai: bool,
@@ -67,18 +65,23 @@ pub struct RobotsTag {
 }
 
 impl RobotsTag {
-    pub fn new() -> Self {
+    pub(super) fn new() -> Self {
         Default::default()
     }
 
-    pub fn with_bot_name(bot_name: Option<HeaderValueString>) -> Self {
+    pub(super) fn new_with_bot_name(bot_name: Option<HeaderValueString>) -> Self {
         Self {
             bot_name,
             ..Default::default()
         }
     }
 
-    pub fn builder() -> RobotsTagBuilder {
+    pub(super) fn add_custom_rule(&mut self, rule: CustomRule) -> &mut Self {
+        self.custom_rules.push(rule);
+        self
+    }
+
+    pub(super) fn builder() -> RobotsTagBuilder {
         RobotsTagBuilder::new()
     }
 
@@ -94,9 +97,8 @@ impl RobotsTag {
     getter_setter!(max_video_preview, u32, optional);
     getter_setter!(no_translate, bool);
     getter_setter!(no_image_index, bool);
-    getter_setter!(unavailable_after, chrono::DateTime<chrono::Utc>, optional);
+    getter_setter!(unavailable_after, ValidDate, optional);
     getter_setter!(no_ai, bool);
     getter_setter!(no_image_ai, bool);
     getter_setter!(spc, bool);
-    getter_setter!(custom_rules, CustomRule, vec);
 }
diff --git a/rama-http/src/headers/x_robots_tag/robots_tag_builder.rs b/rama-http/src/headers/x_robots_tag/robots_tag_builder.rs
index 00cb9b55..ef10a555 100644
--- a/rama-http/src/headers/x_robots_tag/robots_tag_builder.rs
+++ b/rama-http/src/headers/x_robots_tag/robots_tag_builder.rs
@@ -2,16 +2,22 @@ use crate::headers::util::value_string::HeaderValueString;
 use crate::headers::x_robots_tag::custom_rule::CustomRule;
 use crate::headers::x_robots_tag::max_image_preview_setting::MaxImagePreviewSetting;
 use crate::headers::x_robots_tag::robots_tag::RobotsTag;
+use crate::headers::x_robots_tag::valid_date::ValidDate;
 
 macro_rules! builder_field {
     ($field:ident, $type:ty) => {
         paste::paste! {
-            pub fn [<$field>](mut self, [<$field>]: $type) -> Self {
+            pub(super) fn [<$field>](mut self, [<$field>]: $type) -> Self {
                 self.0.[<set_ $field>]([<$field>]);
                 self
             }
 
-            pub fn [<set_ $field>](&mut self, [<$field>]: $type) -> &mut Self {
+            pub(super) fn [<set_ $field>](&mut self, [<$field>]: $type) -> &mut Self {
+                self.0.[<set_ $field>]([<$field>]);
+                self
+            }
+
+            pub(super) fn [<with_ $field>](mut self, [<$field>]: $type) -> Self {
                 self.0.[<set_ $field>]([<$field>]);
                 self
             }
@@ -19,27 +25,30 @@ macro_rules! builder_field {
     };
 }
 
-#[derive(Clone, Debug, Eq, PartialEq, Default)]
-pub struct RobotsTagBuilder<T = ()>(T);
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub(super) struct RobotsTagBuilder<T = ()>(T);
 
 impl RobotsTagBuilder<()> {
-    pub fn new() -> Self {
+    pub(super) fn new() -> Self {
         RobotsTagBuilder(())
     }
 
-    pub fn bot_name(self, bot_name: Option<HeaderValueString>) -> RobotsTagBuilder<RobotsTag> {
-        RobotsTagBuilder(RobotsTag::with_bot_name(bot_name))
+    pub(super) fn bot_name(
+        self,
+        bot_name: Option<HeaderValueString>,
+    ) -> RobotsTagBuilder<RobotsTag> {
+        RobotsTagBuilder(RobotsTag::new_with_bot_name(bot_name))
     }
 }
 
 impl RobotsTagBuilder<RobotsTag> {
-    pub fn add_custom_rule(&mut self, rule: CustomRule) -> &mut Self {
-        self.0.add_custom_rules(rule);
-        self
+    pub(super) fn build(self) -> RobotsTag {
+        self.0
     }
 
-    pub fn build(self) -> RobotsTag {
-        self.0
+    pub(super) fn add_custom_rule(&mut self, rule: CustomRule) -> &mut Self {
+        self.0.add_custom_rule(rule);
+        self
     }
 
     builder_field!(bot_name, HeaderValueString);
@@ -54,7 +63,7 @@ impl RobotsTagBuilder<RobotsTag> {
     builder_field!(max_video_preview, u32);
     builder_field!(no_translate, bool);
     builder_field!(no_image_index, bool);
-    builder_field!(unavailable_after, chrono::DateTime<chrono::Utc>);
+    builder_field!(unavailable_after, ValidDate);
     builder_field!(no_ai, bool);
     builder_field!(no_image_ai, bool);
     builder_field!(spc, bool);
diff --git a/rama-http/src/headers/x_robots_tag/valid_date.rs b/rama-http/src/headers/x_robots_tag/valid_date.rs
new file mode 100644
index 00000000..929c56e8
--- /dev/null
+++ b/rama-http/src/headers/x_robots_tag/valid_date.rs
@@ -0,0 +1,46 @@
+use chrono::{DateTime, Utc};
+use rama_core::error::OpaqueError;
+use std::ops::Deref;
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub(super) struct ValidDate(DateTime<Utc>);
+
+impl ValidDate {
+    pub(super) fn new(date: DateTime<Utc>) -> Result<Self, OpaqueError> {
+        Ok(Self(date))
+    }
+}
+
+impl Deref for ValidDate {
+    type Target = DateTime<Utc>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl From<ValidDate> for DateTime<Utc> {
+    fn from(value: ValidDate) -> Self {
+        value.0
+    }
+}
+
+impl TryFrom<DateTime<Utc>> for ValidDate {
+    type Error = OpaqueError;
+
+    fn try_from(value: DateTime<Utc>) -> Result<Self, Self::Error> {
+        ValidDate::new(value)
+    }
+}
+
+impl AsRef<DateTime<Utc>> for ValidDate {
+    fn as_ref(&self) -> &DateTime<Utc> {
+        &self.0
+    }
+}
+
+impl AsMut<DateTime<Utc>> for ValidDate {
+    fn as_mut(&mut self) -> &mut DateTime<Utc> {
+        &mut self.0
+    }
+}