diff --git a/der/src/asn1/generalized_time.rs b/der/src/asn1/generalized_time.rs
index f7b6f180f..8837917c3 100644
--- a/der/src/asn1/generalized_time.rs
+++ b/der/src/asn1/generalized_time.rs
@@ -37,7 +37,7 @@ impl GeneralizedTime {
     const LENGTH: usize = 15;
 
     /// Create a [`GeneralizedTime`] from a [`DateTime`].
-    pub fn from_date_time(datetime: DateTime) -> Self {
+    pub const fn from_date_time(datetime: DateTime) -> Self {
         Self(datetime)
     }
 
diff --git a/der/src/datetime.rs b/der/src/datetime.rs
index de28d53bb..fd09b6855 100644
--- a/der/src/datetime.rs
+++ b/der/src/datetime.rs
@@ -56,6 +56,18 @@ pub struct DateTime {
 }
 
 impl DateTime {
+    /// This is the maximum date represented by the [`DateTime`]
+    /// This corresponds to: 9999-12-31T23:59:59Z
+    pub const INFINITY: DateTime = DateTime {
+        year: 9999,
+        month: 12,
+        day: 31,
+        hour: 23,
+        minutes: 59,
+        seconds: 59,
+        unix_duration: MAX_UNIX_DURATION,
+    };
+
     /// Create a new [`DateTime`] from the given UTC time components.
     // TODO(tarcieri): checked arithmetic
     #[allow(clippy::integer_arithmetic)]