diff --git a/.github/workflows/default.yml b/.github/workflows/default.yml
index 55eb10f..3100fd9 100644
--- a/.github/workflows/default.yml
+++ b/.github/workflows/default.yml
@@ -28,7 +28,7 @@ jobs:
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'
-          java-version: 20
+          java-version: 21
 
       - uses: gradle/gradle-build-action@v2
 
@@ -83,7 +83,7 @@ jobs:
     runs-on: macos-latest
     strategy:
       matrix:
-        apiVersion: [ 23, 28, 30, 31, 33 ]
+        apiVersion: [ 23, 28, 30, 31, 34 ]
       fail-fast: false
 
     steps:
@@ -94,7 +94,7 @@ jobs:
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'
-          java-version: 20
+          java-version: 21
 
       - uses: gradle/gradle-build-action@v2
 
diff --git a/.github/workflows/dependencies.yml b/.github/workflows/dependencies.yml
index 9bf25c5..faa3514 100644
--- a/.github/workflows/dependencies.yml
+++ b/.github/workflows/dependencies.yml
@@ -29,7 +29,7 @@ jobs:
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'
-          java-version: 20
+          java-version: 21
 
       - uses: gradle/gradle-build-action@v2
 
diff --git a/.github/workflows/publish_release.yml b/.github/workflows/publish_release.yml
index c3956dc..7493044 100644
--- a/.github/workflows/publish_release.yml
+++ b/.github/workflows/publish_release.yml
@@ -24,7 +24,7 @@ jobs:
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'
-          java-version: 20
+          java-version: 21
 
       - uses: gradle/gradle-build-action@v2
 
diff --git a/.github/workflows/run_diffuse.yml b/.github/workflows/run_diffuse.yml
index 1fd1a5d..d5522ca 100644
--- a/.github/workflows/run_diffuse.yml
+++ b/.github/workflows/run_diffuse.yml
@@ -28,7 +28,7 @@ jobs:
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'
-          java-version: 20
+          java-version: 21
 
       - uses: gradle/gradle-build-action@v2
 
diff --git a/.github/workflows/update_tzdb.yml b/.github/workflows/update_tzdb.yml
index df9c4ce..e016141 100644
--- a/.github/workflows/update_tzdb.yml
+++ b/.github/workflows/update_tzdb.yml
@@ -16,7 +16,7 @@ jobs:
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'
-          java-version: 20
+          java-version: 21
 
       - id: current-tzdb-version
         run: |
diff --git a/build.gradle b/build.gradle
index 5e58dd2..93ec8ec 100644
--- a/build.gradle
+++ b/build.gradle
@@ -19,7 +19,7 @@ allprojects {
     }
     pluginManager.withPlugin("kotlin") {
         kotlin {
-            jvmToolchain(20)
+            jvmToolchain(21)
         }
     }
 }