The Calendar hole will go live in approximately 10 days. Why not try and solve it ahead of time?
Leap Years in Haskell in bytes. Achievements Cheevos Holes Languages Medals Miscellaneous All Holes 12 Days of Christmas 24 Game 99 Bottles of Beer Abundant Numbers Abundant Numbers (Long) Arabic to Roman Arithmetic Numbers Arrows Ascending Primes ASCII Table Billiards brainfuck Card Number Validation Catalan Numbers Catalan’s Constant Christmas Trees Collatz CSS Colors Cubes Day of Week DFA Simulator Diamonds Divisors Emirp Numbers Emirp Numbers (Long) Emojify Evil Numbers Evil Numbers (Long) Factorial Factorisation Farey Sequence Fibonacci Fizz Buzz Foo Fizz Buzz Bar Forsyth–Edwards Notation Fractions Game of Life Gijswijt’s Sequence Happy Numbers Happy Numbers (Long) Hexdump Hilbert Curve Intersection Inventory Sequence ISBN Jacobi Symbol Kaprekar Numbers Kolakoski Constant Kolakoski Sequence Leap Years Levenshtein Distance Leyland Numbers ln 2 Look and Say Lucky Numbers Lucky Tickets Mahjong Mandelbrot Maze Medal Tally Minesweeper Morse Decoder Morse Encoder Musical Chords N Queens Niven Numbers Niven Numbers (Long) Number Spiral Odious Numbers Odious Numbers (Long) Ordinal Numbers PalindromemordnilaP Pangram Grep Partition Numbers Pascal’s Triangle Pernicious Numbers Pernicious Numbers (Long) Poker Polyominoes Prime Numbers Prime Numbers (Long) Proximity Grid QR Decoder Quine Recamán Repeating Decimals Reverse Polish Notation Reversi Rijndael S-box Rock-paper-scissors-Spock-lizard Roman to Arabic ROT13 Rule 110 Scrambled Sort Set Seven Segment SI Units Sierpiński Triangle Smith Numbers Spelling Numbers Star Wars GPT Star Wars Opening Crawl Sudoku Sudoku (Fill-in) Ten-pin Bowling Tic-tac-toe Time Distance Tongue-twisters Topological Sort Tower of Hanoi Transpose Sentence Trinomial Triangle United States Vampire Numbers Van Eck Sequence Zeckendorf Representation Zodiac Signs γ λ π τ φ √2 𝑒 Apéry’s Constant Binary Lambda Calculus Calendar Connect Four Continued Fractions Crossword CSS Colors (Inverse) CSS Grid Ellipse Perimeters Flags Floyd-Steinberg Dithering Gray Code Decoder Gray Code Encoder Hexagonal Spiral Highly Composite Numbers Multitap Input NFA Simulator Numbrix Odd Polyomino Tiling p-adic Expansion Polygon Triangulations QR Encoder Quadratic Formula Semiprime Numbers Smooth Numbers Snake Sphenic Numbers Taxicab Numbers Turtle Tutorial All Languages ><> Assembly AWK Bash BASIC Berry brainfuck C C# C++ Civet Clojure COBOL Coconut Common Lisp Crystal D Dart Elixir Erlang F# Factor Forth Fortran Gleam Go GolfScript Groovy Haskell Hexagony J Janet Java JavaScript jq Julia K Kotlin Lua Nim OCaml Pascal Perl PHP PowerShell Prolog Python R Raku Rockstar Ruby Rust Scheme sed SQL Swift Tcl TeX V VimL Wren Zig 05AB1E ALGOL 68 APL Arturo Befunge BQN CJam CoffeeScript Egel Fennel Harbour Hare Haxe Hush Hy iogii Knight Luau Odin Picat Qore Racket Rebol Rexx Scala Squirrel Stax Uiua Umka Vala Vyxal Bytes Chars Scoring Bytes Chars Language All ><> Assembly AWK Bash BASIC Berry brainfuck C C# C++ Civet Clojure COBOL Coconut Common Lisp Crystal D Dart Elixir Erlang F# Factor Forth Fortran Gleam Go GolfScript Groovy Haskell Hexagony J Janet Java JavaScript jq Julia K Kotlin Lua Nim OCaml Pascal Perl PHP PowerShell Prolog Python R Raku Rockstar Ruby Rust Scheme sed SQL Swift Tcl TeX V VimL Wren Zig Experimental Language 05AB1E ALGOL 68 APL Arturo Befunge BQN CJam CoffeeScript Egel Fennel Harbour Hare Haxe Hush Hy iogii Knight Luau Odin Picat Qore Racket Rebol Rexx Scala Squirrel Stax Uiua Umka Vala Vyxal Hole All 12 Days of Christmas 24 Game 99 Bottles of Beer Abundant Numbers Abundant Numbers (Long) Arabic to Roman Arithmetic Numbers Arrows Ascending Primes ASCII Table Billiards brainfuck Card Number Validation Catalan Numbers Catalan’s Constant Christmas Trees Collatz CSS Colors Cubes Day of Week DFA Simulator Diamonds Divisors Emirp Numbers Emirp Numbers (Long) Emojify Evil Numbers Evil Numbers (Long) Factorial Factorisation Farey Sequence Fibonacci Fizz Buzz Foo Fizz Buzz Bar Forsyth–Edwards Notation Fractions Game of Life Gijswijt’s Sequence Happy Numbers Happy Numbers (Long) Hexdump Hilbert Curve Intersection Inventory Sequence ISBN Jacobi Symbol Kaprekar Numbers Kolakoski Constant Kolakoski Sequence Leap Years Levenshtein Distance Leyland Numbers ln 2 Look and Say Lucky Numbers Lucky Tickets Mahjong Mandelbrot Maze Medal Tally Minesweeper Morse Decoder Morse Encoder Musical Chords N Queens Niven Numbers Niven Numbers (Long) Number Spiral Odious Numbers Odious Numbers (Long) Ordinal Numbers PalindromemordnilaP Pangram Grep Partition Numbers Pascal’s Triangle Pernicious Numbers Pernicious Numbers (Long) Poker Polyominoes Prime Numbers Prime Numbers (Long) Proximity Grid QR Decoder Quine Recamán Repeating Decimals Reverse Polish Notation Reversi Rijndael S-box Rock-paper-scissors-Spock-lizard Roman to Arabic ROT13 Rule 110 Scrambled Sort Set Seven Segment SI Units Sierpiński Triangle Smith Numbers Spelling Numbers Star Wars GPT Star Wars Opening Crawl Sudoku Sudoku (Fill-in) Ten-pin Bowling Tic-tac-toe Time Distance Tongue-twisters Topological Sort Tower of Hanoi Transpose Sentence Trinomial Triangle United States Vampire Numbers Van Eck Sequence Zeckendorf Representation Zodiac Signs γ λ π τ φ √2 𝑒 Experimental Hole Apéry’s Constant Binary Lambda Calculus Calendar Connect Four Continued Fractions Crossword CSS Colors (Inverse) CSS Grid Ellipse Perimeters Flags Floyd-Steinberg Dithering Gray Code Decoder Gray Code Encoder Hexagonal Spiral Highly Composite Numbers Multitap Input NFA Simulator Numbrix Odd Polyomino Tiling p-adic Expansion Polygon Triangulations QR Encoder Quadratic Formula Semiprime Numbers Smooth Numbers Snake Sphenic Numbers Taxicab Numbers Turtle Tutorial # Golfer Points Bytes Time Submitted 1st lynn 1,000 49 115ms 12 Apr 2021 1st HPWiz 🇳🇿 1,000 49 114ms 17 Apr 2021 1st xnor-gate 1,000 49 117ms 17 Apr 2021 1st JayXon 🇺🇸 1,000 49 114ms 17 Apr 2021 1st Lydxn 🇨🇦 1,000 49 112ms 13 Nov 2021 1st Sakisan 🇧🇪 1,000 49 120ms 12 Apr 2022 1st ovs-code 🇩🇪 1,000 49 112ms 11 May 2023 8th primo-ppcg 🇹🇭 980 50 115ms 1 Apr 2019 8th jslip 980 50 114ms 2 Apr 2019 8th SirHaswell 980 50 120ms 13 Jun 2019 8th Attero 🇸🇪 980 50 116ms 31 Mar 2020 8th SirBogman 🇺🇸 980 50 122ms 14 Jun 2020 8th aionescu 980 50 115ms 15 Aug 2020 8th GrayJoKing 🇦🇺 980 50 116ms 6 Dec 2020 8th sisyphus-ppcg 🇦🇺 980 50 120ms 20 Mar 2021 8th Shanethegamer 🇺🇸 980 50 120ms 30 Jun 2021 8th laikoni 980 50 111ms 27 Aug 2021 8th Irratix 🇳🇱 980 50 113ms 25 Sep 2021 8th annaproxy 980 50 124ms 7 Jan 2022 8th janbehrens 🇩🇪 980 50 112ms 20 Jul 2022 8th Steffan153 🇫🇮 980 50 120ms 8 Oct 2022 8th alomiF 980 50 120ms 1 Sep 2023 8th jared-hughes 980 50 121ms 7 Jul 2024 8th sean-niemann 🇺🇸 980 50 120ms 7 Jan 2025 8th DialFrost 🇸🇬 980 50 113ms 14 Feb 2025 8th iczelia 🇩🇪 980 50 115ms 16 Oct 2025 8th edsrzf 🇳🇿 980 50 146ms 4 hours ago 28th olivermrose 🇺🇸 961 51 118ms 23 Aug 2021 29th arjanadriaanse 🇳🇱 942 52 121ms 1 Jan 2022 30th yanjs 925 53 119ms 3 Jul 2025 31st marcin7Cd 907 54 112ms 10 Mar 2020 31st andersk 🇺🇸 907 54 113ms 20 Mar 2020 31st kops-cg 907 54 123ms 13 Mar 2025 31st dokutan 907 54 116ms 17 Jul 2025 31st fuzzylojik-golf 🇺🇸 907 54 117ms 14 Sep 2025 36th bforte 891 55 115ms 29 Dec 2018 36th rak1507 🇬🇧 891 55 111ms 24 Sep 2021 36th Bubbler-4 891 55 113ms 16 Nov 2021 36th voytxt 🇨🇿 891 55 144ms 28 Jul 2023 40th treeowl 875 56 118ms 1 Mar 2019 41st somebody1234 845 58 118ms 8 Dec 2018 41st flawr 845 58 110ms 23 Feb 2019 41st boxjelly 845 58 111ms 1 Jan 2021 41st cipharius 845 58 112ms 18 Jan 2021 41st yzhs 🇩🇪 845 58 117ms 24 Jul 2021 41st Natanaelel 🇸🇪 845 58 112ms 11 Sep 2021 41st HallMatthew314 845 58 117ms 14 Feb 2022 41st dteague3989 845 58 115ms 10 Oct 2023 41st roguh 🇬🇹 845 58 113ms 29 Dec 2023 41st tobeannouncd 845 58 118ms 11 Jan 2024 41st inverseLorentz 🇦🇺 845 58 113ms 10 May 2024 52nd ReidZ3 🇺🇸 831 59 113ms 28 Nov 2020 52nd abailey2020 🇺🇸 831 59 118ms 10 Dec 2020 54th user189032 817 60 115ms 29 May 2019 54th exodrifter 🇺🇸 817 60 110ms 25 Oct 2022 56th citsur 790 62 111ms 9 Jun 2019 56th the-zammers 790 62 121ms 19 Oct 2023 56th Yewzir 🇧🇪 790 62 117ms 7 Feb 2024 59th heanyang1 778 63 117ms 31 Jan 2025 59th snoozingnewt 🇨🇦 778 63 118ms 3 Oct 2025 61st hymanimy 766 64 113ms 28 Jul 2021 61st strout 766 64 121ms 15 Aug 2022 63rd juntuu 754 65 112ms 24 Mar 2019 63rd guliyevemil1 🇦🇿 754 65 115ms 17 Apr 2020 63rd brimstonetrader 754 65 113ms 10 Apr 2024 63rd AdamMorris377 754 65 117ms 27 Aug 2024 63rd HolmDev 754 65 115ms 17 Sep 2025 68th Johannesd3 742 66 116ms 1 Jul 2019 68th mhgockel 742 66 112ms 23 Jul 2023 68th epic-programmer-guy 742 66 114ms 25 Dec 2023 71st CatsAreFluffy 731 67 113ms 14 Dec 2022 72nd drbalan 700 70 112ms 20 Jul 2020 72nd Awsute 700 70 109ms 11 Mar 2022 72nd Betuaredead 700 70 113ms 17 Jan 2023 72nd XavierRex 700 70 116ms 13 May 2024 72nd WatMan77 700 70 128ms 26 May 2025 77th TheDrawingCoder-Gamer 690 71 130ms 2 Jul 2025 78th fruno-bulax 681 72 112ms 16 Feb 2019 78th RustemB 🇷🇺 681 72 123ms 25 Aug 2020 78th MeWhenI 🇻🇦 681 72 116ms 10 Oct 2022 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