diff --git a/.gitignore b/.gitignore
index 0a8704c..ab425e6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,113 @@
-build/
-.gradle/
-*.ipr
+
+# Created by https://www.toptal.com/developers/gitignore/api/intellij+all,gradle
+# Edit at https://www.toptal.com/developers/gitignore?templates=intellij+all,gradle
+
+### Intellij+all ###
+# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio, WebStorm and Rider
+# Reference: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839
+
+# User-specific stuff
+.idea/**/workspace.xml
+.idea/**/tasks.xml
+.idea/**/usage.statistics.xml
+.idea/**/dictionaries
+.idea/**/shelf
+
+# Generated files
+.idea/**/contentModel.xml
+
+# Sensitive or high-churn files
+.idea/**/dataSources/
+.idea/**/dataSources.ids
+.idea/**/dataSources.local.xml
+.idea/**/sqlDataSources.xml
+.idea/**/dynamic.xml
+.idea/**/uiDesigner.xml
+.idea/**/dbnavigator.xml
+
+# Gradle
+.idea/**/gradle.xml
+.idea/**/libraries
+
+# Gradle and Maven with auto-import
+# When using Gradle or Maven with auto-import, you should exclude module files,
+# since they will be recreated, and may cause churn.  Uncomment if using
+# auto-import.
+# .idea/artifacts
+# .idea/compiler.xml
+# .idea/jarRepositories.xml
+# .idea/modules.xml
+# .idea/*.iml
+# .idea/modules
+# *.iml
+# *.ipr
+
+# CMake
+cmake-build-*/
+
+# Mongo Explorer plugin
+.idea/**/mongoSettings.xml
+
+# File-based project format
+*.iws
+
+# IntelliJ
+out/
+
+# mpeltonen/sbt-idea plugin
+.idea_modules/
+
+# JIRA plugin
+atlassian-ide-plugin.xml
+
+# Cursive Clojure plugin
+.idea/replstate.xml
+
+# Crashlytics plugin (for Android Studio and IntelliJ)
+com_crashlytics_export_strings.xml
+crashlytics.properties
+crashlytics-build.properties
+fabric.properties
+
+# Editor-based Rest Client
+.idea/httpRequests
+
+# Android studio 3.1+ serialized cache file
+.idea/caches/build_file_checksums.ser
+
+### Intellij+all Patch ###
+# Ignores the whole .idea folder and all .iml files
+# See https://github.com/joeblau/gitignore.io/issues/186 and https://github.com/joeblau/gitignore.io/issues/360
+
+.idea/
+
+# Reason: https://github.com/joeblau/gitignore.io/issues/186#issuecomment-249601023
+
 *.iml
-*.iws
\ No newline at end of file
+modules.xml
+.idea/misc.xml
+*.ipr
+
+# Sonarlint plugin
+.idea/sonarlint
+
+### Gradle ###
+.gradle
+build/
+
+# Ignore Gradle GUI config
+gradle-app.setting
+
+# Avoid ignoring Gradle wrapper jar file (.jar files are usually ignored)
+!gradle-wrapper.jar
+
+# Cache of project
+.gradletasknamecache
+
+# # Work around https://youtrack.jetbrains.com/issue/IDEA-116898
+# gradle/wrapper/gradle-wrapper.properties
+
+### Gradle Patch ###
+**/build/
+
+# End of https://www.toptal.com/developers/gitignore/api/intellij+all,gradle
diff --git a/build.gradle b/build.gradle
deleted file mode 100644
index 888e0b1..0000000
--- a/build.gradle
+++ /dev/null
@@ -1,37 +0,0 @@
-buildscript {
-  ext {
-    versions = [
-        hamkrest: "1.4.0.0",
-        junit: "1.0.0-M4",
-        jupiter: "5.0.0-M4",
-        kotlin: "1.1.2",
-        spek: "1.1.1"
-    ]
-  }
-
-  repositories {
-    jcenter()
-  }
-
-  dependencies {
-    classpath "org.junit.platform:junit-platform-gradle-plugin:${versions.junit}"
-    classpath "com.netflix.nebula:nebula-kotlin-plugin:${versions.kotlin}"
-  }
-}
-
-subprojects {
-  apply plugin: "java"
-  apply plugin: "org.junit.platform.gradle.plugin"
-
-  repositories {
-    jcenter()
-  }
-
-  dependencies {
-    testCompile "org.junit.jupiter:junit-jupiter-api:${versions.jupiter}"
-    testRuntime "org.junit.jupiter:junit-jupiter-engine:${versions.jupiter}"
-  }
-
-  sourceCompatibility = 1.8
-  targetCompatibility = 1.8
-}
\ No newline at end of file
diff --git a/build.gradle.kts b/build.gradle.kts
new file mode 100644
index 0000000..e69de29
diff --git a/buildSrc/build.gradle.kts b/buildSrc/build.gradle.kts
new file mode 100644
index 0000000..9dcdc72
--- /dev/null
+++ b/buildSrc/build.gradle.kts
@@ -0,0 +1,8 @@
+
+plugins {
+    `kotlin-dsl`
+}
+
+repositories {
+    gradlePluginPortal() // so that external plugins can be resolved in dependencies section
+}
diff --git a/buildSrc/src/main/kotlin/test-clock-conventions.gradle.kts b/buildSrc/src/main/kotlin/test-clock-conventions.gradle.kts
new file mode 100644
index 0000000..bf22cf5
--- /dev/null
+++ b/buildSrc/src/main/kotlin/test-clock-conventions.gradle.kts
@@ -0,0 +1,19 @@
+plugins {
+    java
+}
+
+repositories {
+    mavenCentral()
+    jcenter()
+}
+val junit5Version: String by project
+
+dependencies {
+    testImplementation("org.junit.jupiter:junit-jupiter-api:$junit5Version")
+    testRuntimeOnly("org.junit.jupiter:junit-jupiter-engine:$junit5Version")
+}
+
+java {
+    sourceCompatibility = JavaVersion.VERSION_1_8
+    targetCompatibility = JavaVersion.VERSION_1_8
+}
diff --git a/gradle.properties b/gradle.properties
new file mode 100644
index 0000000..80a1d28
--- /dev/null
+++ b/gradle.properties
@@ -0,0 +1,2 @@
+junit5Version = 5.7.0
+kotestVersion = 4.3.2
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
index 85aef70..666595e 100644
Binary files a/gradle/wrapper/gradle-wrapper.jar and b/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 9e89b67..4684e09 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,6 +1,6 @@
-#Fri May 19 21:40:25 PDT 2017
+#Thu Dec 31 12:18:29 CST 2020
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-3.5-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.7.1-bin.zip
diff --git a/settings.gradle b/settings.gradle
deleted file mode 100644
index bad7f05..0000000
--- a/settings.gradle
+++ /dev/null
@@ -1,16 +0,0 @@
-include "test-clock-core",
-    "test-clock-kotlin"
-
-rootProject.name = "test-clock"
-
-def setBuildFile(project) {
-  project.buildFileName = "${project.name}.gradle"
-  project.children.each {
-    setBuildFile(it)
-  }
-}
-
-rootProject.children.each {
-  setBuildFile it
-}
-
diff --git a/settings.gradle.kts b/settings.gradle.kts
new file mode 100644
index 0000000..ed8f3f7
--- /dev/null
+++ b/settings.gradle.kts
@@ -0,0 +1,4 @@
+include("test-clock-core","test-clock-kotlin")
+
+rootProject.name = "test-clock"
+
diff --git a/test-clock-core/build.gradle.kts b/test-clock-core/build.gradle.kts
new file mode 100644
index 0000000..98f140d
--- /dev/null
+++ b/test-clock-core/build.gradle.kts
@@ -0,0 +1,7 @@
+plugins {
+  id("test-clock-conventions")
+}
+
+dependencies {
+  implementation("com.google.code.findbugs:jsr305:3.0.2")
+}
diff --git a/test-clock-core/src/test/java/io/github/robfletcher/time/MutableClockTests.java b/test-clock-core/src/test/java/io/github/robfletcher/time/MutableClockTests.java
index dffc77d..ad10bbe 100644
--- a/test-clock-core/src/test/java/io/github/robfletcher/time/MutableClockTests.java
+++ b/test-clock-core/src/test/java/io/github/robfletcher/time/MutableClockTests.java
@@ -55,4 +55,4 @@ void canChangeInstant() {
     testClock.instant(fixedClock.instant());
     assertEquals(testClock.instant(), fixedClock.instant());
   }
-}
\ No newline at end of file
+}
diff --git a/test-clock-core/test-clock-core.gradle b/test-clock-core/test-clock-core.gradle
deleted file mode 100644
index a7a1f40..0000000
--- a/test-clock-core/test-clock-core.gradle
+++ /dev/null
@@ -1,3 +0,0 @@
-dependencies {
-  compile "com.google.code.findbugs:jsr305:3.0.2"
-}
\ No newline at end of file
diff --git a/test-clock-kotlin/build.gradle.kts b/test-clock-kotlin/build.gradle.kts
new file mode 100644
index 0000000..78f82fd
--- /dev/null
+++ b/test-clock-kotlin/build.gradle.kts
@@ -0,0 +1,19 @@
+plugins {
+    kotlin("jvm") version "1.4.21"
+    id("test-clock-conventions")
+}
+repositories {
+    mavenCentral()
+}
+
+val kotestVersion: String by project
+
+dependencies {
+    implementation(project(":test-clock-core"))
+    testImplementation("io.kotest:kotest-runner-junit5:$kotestVersion")
+    testImplementation("io.kotest:kotest-assertions-core:$kotestVersion")
+}
+
+tasks.withType<Test> {
+    useJUnitPlatform()
+}
diff --git a/test-clock-kotlin/src/test/kotlin/io/github/robfletcher/time/MutableClockSpec.kt b/test-clock-kotlin/src/test/kotlin/io/github/robfletcher/time/MutableClockSpec.kt
index ef3a903..b76af44 100644
--- a/test-clock-kotlin/src/test/kotlin/io/github/robfletcher/time/MutableClockSpec.kt
+++ b/test-clock-kotlin/src/test/kotlin/io/github/robfletcher/time/MutableClockSpec.kt
@@ -1,73 +1,52 @@
 package io.github.robfletcher.time
 
-import com.natpryce.hamkrest.equalTo
-import com.natpryce.hamkrest.should.shouldMatch
-import org.jetbrains.spek.api.dsl.describe
-import org.jetbrains.spek.api.dsl.given
-import org.jetbrains.spek.api.dsl.it
-import org.jetbrains.spek.api.dsl.on
-import org.jetbrains.spek.api.lifecycle.CachingMode.SCOPE
-import org.jetbrains.spek.subject.SubjectSpek
+import io.kotest.core.spec.style.DescribeSpec
+import io.kotest.matchers.shouldBe
+import io.kotest.matchers.shouldNotBe
 import java.time.Clock
-import java.time.Clock.fixed
 import java.time.Duration
 import java.time.Instant.EPOCH
 import java.time.ZoneOffset.MAX
 import java.time.ZoneOffset.MIN
 
-object MutableClockSpec : SubjectSpek<MutableClock>({
+class MutableClockSpec : DescribeSpec({
 
-  var fixedClock: Clock? = null
+    var fixedClock: Clock? = null
 
-  beforeGroup {
-    fixedClock = Clock.fixed(subject.instant(), subject.zone)
-  }
-
-  describe("mutable clock") {
-    subject(SCOPE) {
-      mutableClock()
-    }
-
-    it("is equal to a fixed clock with the same instant and zone") {
-      subject shouldMatch equalTo(fixedClock)
-    }
-
-    it("is not equal to a fixed clock with a different instant") {
-      subject shouldMatch !equalTo(fixed(subject.instant.plusMillis(1), subject.zone))
-    }
-
-    it("is not equal to a fixed clock with a different time zone") {
-      subject.withZone(MIN) shouldMatch !equalTo(fixedClock!!.withZone(MAX))
-    }
-
-    describe("advancing time") {
-      on("advancing the clock") {
-        subject += Duration.ofHours(1)
-      }
-
-      it("changes the instant reported by the clock") {
-        subject.instant shouldMatch equalTo(fixedClock!!.instant() + Duration.ofHours(1))
-      }
+    describe("mutable clock") {
+        lateinit var subject: MutableClock
+        beforeEach {
+            subject = mutableClock()
+            fixedClock = Clock.fixed(subject.instant(), subject.zone)
+        }
 
-      given("and advanced again") {
-        on("advancing the clock again") {
-          subject += Duration.ofHours(1)
+        it("is equal to a fixed clock with the same instant and zone") {
+            subject shouldBe fixedClock
         }
 
-        it("changes the instant reported by the clock") {
-          subject.instant shouldMatch equalTo(fixedClock!!.instant() + Duration.ofHours(2))
+        it("is not equal to a fixed clock with a different instant") {
+            subject shouldNotBe Clock.fixed(subject.instant.plusMillis(1), subject.zone)
         }
-      }
-    }
 
-    describe("changing the instant") {
-      on("changing the instant") {
-        subject.instant = EPOCH
-      }
+        it("is not equal to a fixed clock with a different time zone") {
+            subject.withZone(MIN) shouldNotBe fixedClock!!.withZone(MAX)
+        }
 
-      it("returns the new instant") {
-        subject.instant() shouldMatch equalTo(EPOCH)
-      }
+        describe("advancing time") {
+            it("changes the instant reported by the clock") {
+                subject += Duration.ofHours(1)
+                subject.instant shouldBe fixedClock!!.instant() + Duration.ofHours(1)
+            }
+
+            describe("changing the instant") {
+                beforeEach {
+                    subject.instant = EPOCH
+
+                }
+                it("returns the new instant") {
+                    subject.instant() shouldBe EPOCH
+                }
+            }
+        }
     }
-  }
-})
\ No newline at end of file
+})
diff --git a/test-clock-kotlin/test-clock-kotlin.gradle b/test-clock-kotlin/test-clock-kotlin.gradle
deleted file mode 100644
index 4e114d7..0000000
--- a/test-clock-kotlin/test-clock-kotlin.gradle
+++ /dev/null
@@ -1,39 +0,0 @@
-apply plugin: "nebula.kotlin"
-
-repositories {
-  maven { url "http://dl.bintray.com/jetbrains/spek" }
-}
-
-dependencies {
-  compile project(":test-clock-core")
-  testCompile "org.jetbrains.spek:spek-api:${versions.spek}"
-  testCompile "org.jetbrains.spek:spek-subject-extension:${versions.spek}"
-  testCompile "com.natpryce:hamkrest:${versions.hamkrest}"
-  testRuntime "org.jetbrains.spek:spek-junit-platform-engine:${versions.spek}"
-}
-
-configurations.all {
-  resolutionStrategy {
-    eachDependency { details ->
-      if (details.requested.group == "org.jetbrains.kotlin") {
-        details.useVersion versions.kotlin
-      }
-    }
-  }
-}
-
-compileKotlin {
-  kotlinOptions {
-    languageVersion = VersionNumber.parse(versions.kotlin).with {
-      "${it.major}.${it.minor}"
-    }
-  }
-}
-
-junitPlatform {
-  filters {
-    engines {
-      include "spek"
-    }
-  }
-}