diff --git a/src/main/java/eu/m724/wtapi/provider/Providers.java b/src/main/java/eu/m724/wtapi/provider/Providers.java
index efc1823..0dfe691 100644
--- a/src/main/java/eu/m724/wtapi/provider/Providers.java
+++ b/src/main/java/eu/m724/wtapi/provider/Providers.java
@@ -3,7 +3,7 @@ package eu.m724.wtapi.provider;
 import eu.m724.wtapi.provider.exception.NoSuchProviderException;
 import eu.m724.wtapi.provider.thunder.ThunderProvider;
 import eu.m724.wtapi.provider.thunder.impl.blitzortung.BlitzortungProvider;
-import eu.m724.wtapi.provider.twilight.ApproximateTwilightTimeProvider;
+import eu.m724.wtapi.provider.twilight.impl.approximate.ApproximateTwilightTimeProvider;
 import eu.m724.wtapi.provider.twilight.TwilightTimeProvider;
 import eu.m724.wtapi.provider.weather.WeatherProvider;
 import eu.m724.wtapi.provider.weather.impl.openweathermap.OpenWeatherMapProvider;
diff --git a/src/main/java/eu/m724/wtapi/provider/twilight/impl/approximate/ApproximateTwilightTimeCache.java b/src/main/java/eu/m724/wtapi/provider/twilight/impl/approximate/ApproximateTwilightTimeCache.java
new file mode 100644
index 0000000..4187eea
--- /dev/null
+++ b/src/main/java/eu/m724/wtapi/provider/twilight/impl/approximate/ApproximateTwilightTimeCache.java
@@ -0,0 +1,9 @@
+package eu.m724.wtapi.provider.twilight.impl.approximate;
+
+import eu.m724.wtapi.provider.twilight.TwilightTimeCache;
+
+import java.time.LocalDate;
+
+public record ApproximateTwilightTimeCache(LocalDate date, double equationOfTime,
+                                           double declination) implements TwilightTimeCache {
+}
diff --git a/src/main/java/eu/m724/wtapi/provider/twilight/ApproximateTwilightTimeProvider.java b/src/main/java/eu/m724/wtapi/provider/twilight/impl/approximate/ApproximateTwilightTimeProvider.java
similarity index 64%
rename from src/main/java/eu/m724/wtapi/provider/twilight/ApproximateTwilightTimeProvider.java
rename to src/main/java/eu/m724/wtapi/provider/twilight/impl/approximate/ApproximateTwilightTimeProvider.java
index 790fc11..663d73b 100644
--- a/src/main/java/eu/m724/wtapi/provider/twilight/ApproximateTwilightTimeProvider.java
+++ b/src/main/java/eu/m724/wtapi/provider/twilight/impl/approximate/ApproximateTwilightTimeProvider.java
@@ -1,7 +1,9 @@
-package eu.m724.wtapi.provider.twilight;
+package eu.m724.wtapi.provider.twilight.impl.approximate;
 
 import eu.m724.wtapi.object.Coordinates;
 import eu.m724.wtapi.object.Twilight;
+import eu.m724.wtapi.provider.twilight.CacheableTwilightTimeProvider;
+import eu.m724.wtapi.provider.twilight.TwilightTimeCache;
 
 import java.time.Duration;
 import java.time.LocalDate;
@@ -9,29 +11,16 @@ import java.time.LocalDate;
 import static java.lang.Math.*;
 
 /**
- * Calculates approximate sunrise and sunset times
- * Usually off by a few minutes, except the Poles which, during polar days, are up to few hours inaccurate
- * Adapted from: <a href="https://gml.noaa.gov/grad/solcalc/solareqns.PDF">https://gml.noaa.gov/grad/solcalc/solareqns.PDF</a>
+ * Calculates approximate sunrise and sunset times<br>
+ * Usually off by a few minutes, except the Poles which, during polar days, are up to few hours inaccurate<br>
+ * I don't know why, I just copied stuff and maybe transformed a bit, I don't actually understand the topic<br>
+ * Source: <a href="https://gml.noaa.gov/grad/solcalc/solareqns.PDF">https://gml.noaa.gov/grad/solcalc/solareqns.PDF</a>
  */
-public class ApproximateTwilightTimeProvider extends TwilightTimeProvider {
+public class ApproximateTwilightTimeProvider extends CacheableTwilightTimeProvider<ApproximateTwilightTimeCache> {
     @Override
-    public Twilight calculateTwilightTime(LocalDate date, Coordinates coordinates) {
-        int dayOfYear = date.getDayOfYear() - 1; // -1 because we have to start from zero
-        // 2 * PI / 365 = 0.01721420632103996
-        double fractionalYear = 0.01721420632103996 * dayOfYear;
-
-        double equationOfTime = 229.18 * (0.000075
-                + 0.001868 * cos(fractionalYear)
-                - 0.032077 * sin(fractionalYear)
-                - 0.014615 * cos(2 * fractionalYear)
-                - 0.040849 * sin(2 * fractionalYear));
-        double declination = 0.006918
-                - 0.399912 * cos(fractionalYear)
-                + 0.070257 * sin(fractionalYear)
-                - 0.006758 * cos(2 * fractionalYear)
-                + 0.000907 * sin(2 * fractionalYear)
-                - 0.002697 * cos(3 * fractionalYear)
-                + 0.00148 * sin(3 * fractionalYear);
+    public Twilight calculateTwilightTime(ApproximateTwilightTimeCache cache, Coordinates coordinates) {
+        double declination = cache.declination();
+        double equationOfTime = cache.equationOfTime();
 
         double latRad = toRadians(coordinates.latitude);
         // 90.833 deg = 1.5853349194640094 rad
@@ -53,4 +42,30 @@ public class ApproximateTwilightTimeProvider extends TwilightTimeProvider {
                 Duration.ofMillis((long) (sunset * 60000))
         );
     }
+
+    @Override
+    public ApproximateTwilightTimeCache initializeCache(LocalDate date) {
+        int dayOfYear = date.getDayOfYear() - 1; // -1 because we have to start from zero
+        // 2 * PI / 365 = 0.01721420632103996
+        double fractionalYear = 0.01721420632103996 * dayOfYear;
+
+        double equationOfTime = 229.18 * (0.000075
+                + 0.001868 * cos(fractionalYear)
+                - 0.032077 * sin(fractionalYear)
+                - 0.014615 * cos(2 * fractionalYear)
+                - 0.040849 * sin(2 * fractionalYear));
+        double declination = 0.006918
+                - 0.399912 * cos(fractionalYear)
+                + 0.070257 * sin(fractionalYear)
+                - 0.006758 * cos(2 * fractionalYear)
+                + 0.000907 * sin(2 * fractionalYear)
+                - 0.002697 * cos(3 * fractionalYear)
+                + 0.00148 * sin(3 * fractionalYear);
+
+        return new ApproximateTwilightTimeCache(
+                date,
+                equationOfTime,
+                declination
+        );
+    }
 }
diff --git a/src/test/java/eu/m724/wtapi/twilight/ApproximateTwilightTimeTest.java b/src/test/java/eu/m724/wtapi/twilight/ApproximateTwilightTimeTest.java
index b15d861..0578096 100644
--- a/src/test/java/eu/m724/wtapi/twilight/ApproximateTwilightTimeTest.java
+++ b/src/test/java/eu/m724/wtapi/twilight/ApproximateTwilightTimeTest.java
@@ -2,12 +2,13 @@ package eu.m724.wtapi.twilight;
 
 import eu.m724.wtapi.object.Coordinates;
 import eu.m724.wtapi.object.Twilight;
-import eu.m724.wtapi.provider.twilight.ApproximateTwilightTimeProvider;
+import eu.m724.wtapi.provider.twilight.impl.approximate.ApproximateTwilightTimeProvider;
 import eu.m724.wtapi.provider.twilight.TwilightTimeProvider;
 import org.junit.Test;
 
 import java.time.LocalDate;
 
+// TODO also test cached
 public class ApproximateTwilightTimeTest {
     /**
      * Acceptable discrepancy in minutes