diff --git a/index.js b/index.js
index 9577212..4992d91 100644
--- a/index.js
+++ b/index.js
@@ -342,12 +342,12 @@ module.exports = class CachePolicy {
     }
 
     _serverDate() {
-        const dateValue = Date.parse(this._resHeaders.date);
-        if (isFinite(dateValue)) {
+        const serverDate = Date.parse(this._resHeaders.date);
+        if (isFinite(serverDate)) {
             const maxClockDrift = 8 * 3600 * 1000;
-            const clockDrift = Math.abs(this._responseTime - dateValue);
+            const clockDrift = Math.abs(this._responseTime - serverDate);
             if (clockDrift < maxClockDrift) {
-                return dateValue;
+                return serverDate;
             }
         }
         return this._responseTime;
@@ -419,22 +419,22 @@ module.exports = class CachePolicy {
 
         const defaultMinTtl = this._rescc.immutable ? this._immutableMinTtl : 0;
 
-        const dateValue = this._serverDate();
+        const serverDate = this._serverDate();
         if (this._resHeaders.expires) {
             const expires = Date.parse(this._resHeaders.expires);
             // A cache recipient MUST interpret invalid date formats, especially the value "0", as representing a time in the past (i.e., "already expired").
-            if (Number.isNaN(expires) || expires < dateValue) {
+            if (Number.isNaN(expires) || expires < serverDate) {
                 return 0;
             }
-            return Math.max(defaultMinTtl, (expires - dateValue) / 1000);
+            return Math.max(defaultMinTtl, (expires - serverDate) / 1000);
         }
 
         if (this._resHeaders['last-modified']) {
             const lastModified = Date.parse(this._resHeaders['last-modified']);
-            if (isFinite(lastModified) && dateValue > lastModified) {
+            if (isFinite(lastModified) && serverDate > lastModified) {
                 return Math.max(
                     defaultMinTtl,
-                    ((dateValue - lastModified) / 1000) * this._cacheHeuristic
+                    ((serverDate - lastModified) / 1000) * this._cacheHeuristic
                 );
             }
         }