diff --git a/src/Utils.kt b/src/Utils.kt
index 879a2c7..87aec90 100644
--- a/src/Utils.kt
+++ b/src/Utils.kt
@@ -2,7 +2,9 @@ import java.io.File
 import java.math.BigInteger
 import java.security.MessageDigest
 
-private fun openFile(day: Int, name: String) = File("src/day%02d".format(day), "$name.txt")
+var year: Int = 2021
+
+private fun openFile(day: Int, name: String) = File("src/year%4d/day%02d".format(year, day), "$name.txt")
 
 /**
  * Reads lines from the given input txt file.
diff --git a/src/day01/Day01.kt b/src/year2021/day01/Day01.kt
similarity index 83%
rename from src/day01/Day01.kt
rename to src/year2021/day01/Day01.kt
index 980d48a..c1843b5 100644
--- a/src/day01/Day01.kt
+++ b/src/year2021/day01/Day01.kt
@@ -1,4 +1,4 @@
-package day01
+package year2021.day01
 
 import readInputAsInts
 
@@ -6,7 +6,7 @@ fun main() {
     fun part1(input: List<Int>): Int = input.windowed(2).count { it[0] < it[1] }
     fun part2(input: List<Int>): Int = input.windowed(4).count { it[0] < it[3] }
 
-    val testInput = readInputAsInts(1, "test_input")
+    val testInput = readInputAsInts(1, "sample")
     val input = readInputAsInts(1, "input")
 
     check(part1(testInput) == 7)
diff --git a/src/day01/test_input.txt b/src/year2021/day01/sample.txt
similarity index 100%
rename from src/day01/test_input.txt
rename to src/year2021/day01/sample.txt
diff --git a/src/day02/Day02.kt b/src/year2021/day02/Day02.kt
similarity index 96%
rename from src/day02/Day02.kt
rename to src/year2021/day02/Day02.kt
index 4ae3317..4e8a458 100644
--- a/src/day02/Day02.kt
+++ b/src/year2021/day02/Day02.kt
@@ -1,4 +1,4 @@
-package day02
+package year2021.day02
 
 import readInput
 
@@ -50,7 +50,7 @@ fun part2(input: List<Instruction>): Int {
 }
 
 fun main() {
-    val testInput = toCommands(readInput(2, "test_input"))
+    val testInput = toCommands(readInput(2, "sample"))
     val input = toCommands(readInput(2, "input"))
 
     check(part1(testInput) == 150)
diff --git a/src/day02/test_input.txt b/src/year2021/day02/sample.txt
similarity index 100%
rename from src/day02/test_input.txt
rename to src/year2021/day02/sample.txt
diff --git a/src/day03/Day03.kt b/src/year2021/day03/Day03.kt
similarity index 94%
rename from src/day03/Day03.kt
rename to src/year2021/day03/Day03.kt
index 2edeedd..18a7852 100644
--- a/src/day03/Day03.kt
+++ b/src/year2021/day03/Day03.kt
@@ -1,4 +1,4 @@
-package day03
+package year2021.day03
 
 import readInput
 
@@ -44,7 +44,7 @@ fun part2(input: List<List<Int>>): Int {
 }
 
 fun main() {
-    val testInput = toBits(readInput(3, "test_input"))
+    val testInput = toBits(readInput(3, "sample"))
     val input = toBits(readInput(3, "input"))
 
     check(part1(testInput) == 198)
diff --git a/src/day03/test_input.txt b/src/year2021/day03/sample.txt
similarity index 100%
rename from src/day03/test_input.txt
rename to src/year2021/day03/sample.txt
diff --git a/src/day04/Day04.kt b/src/year2021/day04/Day04.kt
similarity index 97%
rename from src/day04/Day04.kt
rename to src/year2021/day04/Day04.kt
index 9d66b63..cc73f64 100644
--- a/src/day04/Day04.kt
+++ b/src/year2021/day04/Day04.kt
@@ -1,4 +1,4 @@
-package day04
+package year2021.day04
 
 import readInput
 
@@ -75,7 +75,7 @@ fun part2(input: Bingo): Int {
 }
 
 fun main() {
-    val testInput = Bingo(readInput(4, "test_input"))
+    val testInput = Bingo(readInput(4, "sample"))
     val input = Bingo(readInput(4, "input"))
 
     check(part1(testInput) == 4512)
diff --git a/src/day04/test_input.txt b/src/year2021/day04/sample.txt
similarity index 100%
rename from src/day04/test_input.txt
rename to src/year2021/day04/sample.txt
diff --git a/src/day05/Day05.kt b/src/year2021/day05/Day05.kt
similarity index 95%
rename from src/day05/Day05.kt
rename to src/year2021/day05/Day05.kt
index f792482..f2799d9 100644
--- a/src/day05/Day05.kt
+++ b/src/year2021/day05/Day05.kt
@@ -1,4 +1,4 @@
-package day05
+package year2021.day05
 
 import readInput
 
@@ -56,7 +56,7 @@ fun findOverlaps(input: List<Vector>): Int {
 }
 
 fun main() {
-    val testInput = readInput(5, "test_input").map { readVector(it) }
+    val testInput = readInput(5, "sample").map { readVector(it) }
     val input = readInput(5, "input").map { readVector(it) }
 
     check(findOverlaps(testInput.filter { it.horizontalOrVertical }) == 5)
diff --git a/src/day05/test_input.txt b/src/year2021/day05/sample.txt
similarity index 100%
rename from src/day05/test_input.txt
rename to src/year2021/day05/sample.txt
diff --git a/src/day06/Day06.kt b/src/year2021/day06/Day06.kt
similarity index 86%
rename from src/day06/Day06.kt
rename to src/year2021/day06/Day06.kt
index 83c5dd2..a7d39db 100644
--- a/src/day06/Day06.kt
+++ b/src/year2021/day06/Day06.kt
@@ -1,4 +1,4 @@
-package day06
+package year2021.day06
 
 import readInputAsCommaSeparatedInts
 
@@ -11,7 +11,7 @@ fun howManyAfter(input: List<Int>, days: Int): Long =
         .sum()
 
 fun main() {
-    val testInput = readInputAsCommaSeparatedInts(6, "test_input")
+    val testInput = readInputAsCommaSeparatedInts(6, "sample")
     val input = readInputAsCommaSeparatedInts(6, "input")
 
     check(howManyAfter(testInput, 80) == 5934.toLong())
diff --git a/src/day06/test_input.txt b/src/year2021/day06/sample.txt
similarity index 100%
rename from src/day06/test_input.txt
rename to src/year2021/day06/sample.txt
diff --git a/src/day07/Day07.kt b/src/year2021/day07/Day07.kt
similarity index 88%
rename from src/day07/Day07.kt
rename to src/year2021/day07/Day07.kt
index 09400d6..42aec12 100644
--- a/src/day07/Day07.kt
+++ b/src/year2021/day07/Day07.kt
@@ -1,4 +1,4 @@
-package day07
+package year2021.day07
 
 import readInputAsCommaSeparatedInts
 import kotlin.math.absoluteValue
@@ -20,7 +20,7 @@ fun part2(input: List<Int>): Int = (input.average().toInt()).let { average ->
 }
 
 fun main() {
-    val testInput = readInputAsCommaSeparatedInts(7, "test_input").sorted()
+    val testInput = readInputAsCommaSeparatedInts(7, "sample").sorted()
     val input = readInputAsCommaSeparatedInts(7, "input").sorted()
 
     check(part1(testInput) == 37)
diff --git a/src/day07/test_input.txt b/src/year2021/day07/sample.txt
similarity index 100%
rename from src/day07/test_input.txt
rename to src/year2021/day07/sample.txt