diff --git a/src/ic_backend/src/id_token.rs b/src/ic_backend/src/id_token.rs
index b782c8e..6cec8d4 100644
--- a/src/ic_backend/src/id_token.rs
+++ b/src/ic_backend/src/id_token.rs
@@ -5,7 +5,7 @@ use serde::{Deserialize, Serialize};
 
 use crate::{
     state,
-    utils::{base64_decode, unix_timestamp},
+    utils::{base64_decode, unix_timestamp, NANOS_IN_SECONDS},
 };
 
 /// The maximum age of an ID token (checked against the `iat` claim).
@@ -24,7 +24,9 @@ pub type IdTokenResult<T> = std::result::Result<T, ErrorKind>;
 pub struct JWTClaims {
     pub iss: String,
     pub aud: String,
+    /// Issued at (seconds since unix epoch)
     pub iat: u64,
+    /// Expires at (seconds since unix epoch)
     pub exp: u64,
     pub sub: String,
     pub nonce: String,
@@ -32,7 +34,7 @@ pub struct JWTClaims {
 
 impl JWTClaims {
     pub fn expiration_timestamp_ns(&self) -> u64 {
-        self.exp * 1_000_000_000
+        self.exp * NANOS_IN_SECONDS
     }
 
     pub fn validate(&self) -> Result<(), ValidationError> {
diff --git a/src/ic_backend/src/utils.rs b/src/ic_backend/src/utils.rs
index 6440d8a..ca9b890 100644
--- a/src/ic_backend/src/utils.rs
+++ b/src/ic_backend/src/utils.rs
@@ -6,9 +6,11 @@ use jsonwebtoken_rustcrypto::errors::ErrorKind;
 
 use crate::id_token::IdTokenResult;
 
+pub const NANOS_IN_SECONDS: u64 = 1_000_000_000;
+
 /// Returns the current unix timestamp in seconds
 pub fn unix_timestamp() -> u64 {
-    time() / 1_000_000_000
+    time() / NANOS_IN_SECONDS
 }
 
 pub fn base64_decode(input: &str) -> IdTokenResult<Vec<u8>> {