Is it Christmas?

Question

Challenge

Given that Christmas is:

• December
• Month 12
• Day 25

Every year, determine today's date, and whether or not today is Christmas. If it is Christmas, you must print "It's Christmas". If it is not Christmas, you must somehow wait until Christmas and then print "It's Christmas".

Example

From this Stack Overflow Question

import time
while time.strftime("%b, %d", time.localtime()) != "Dec, 25":
    time.sleep(60)
print "It's Christmas"

Python in 115 Characters

Rules

Here are the rules:

• Assume that the computer's clock is always right.
• Your code must be able to be started at any time.
• Your code must print "It's Christmas" on Christmas.
• Looping is certainly not necessary, but once started your code should not stop until it has printed.
• Shortest code wins.

Answer 1

Unix, 39 bytes

echo{,} "It\'s christmas"|at -t12252359

With help from Dennis, thanks for that.

Answer 2

Perl + Unix, 40 chars

1until`date`=~/c 25/;say"It's Christmas"

This is the same as J B's Perl solution, except that I save a few chars by using the external date command instead of Perl's localtime.

Answer 3

PowerShell, 45 46 chars

for(;(date).date-ne'12/25'){}"It's Christmas"

It's certainly not very power-efficient, so a laptop battery might die before Christmas (reason to wish for a new one, maybe). But not sleeping is definitely shorter.

This is also locale-agnostic. And thanks to Jaykul for a nice trick in reducing this further.

Abusing the rules a bit, 45 chars

for(){"It's Christmas"*((date)-like'12/25*')}

This will print empty lines until it's Christmas, upon which it will print “It's Christmas”.

It ...

• ... can be started at any time.
• ... prints “It's Christmas” on Christmas. Several times. The whole day long. (The rules didn't say anything about how often it may be printed.)
• ... does not print “It's Christmas” on not-Christmas (although it prints an empty line in that case; can be rectified by sacrificing another character, but then this gains nothing over the more sane solution above).
• ... does not ever stop (not even after it has printed “It's Christmas” but definitely not before).

Answer 4

PostScript, 90

(%Calendar%)currentdevparams begin{Month 12 eq Day 25 eq and{exit}if}loop(It's Christmas)=

Don't run on a printer, it doesn't print a page, and it will only DoS your printer until Christmas day. Then again, getting your printer back would be a nice present.

Answer 5

Mathematica, 47

While[Date[][[2;;3]]!={12,25}];"It's Christmas"

Answer 6

Perl, 44 45

perl -E'1until localtime=~/c 25/;say"It's Christmas"'

Wouldn't GMT time be sufficient? (3 characters off ;-)

Answer 7

Perl, 45

{localtime=~/c 25/&&die"It's Christmas";redo}

Perl, 44

using ternary operator (Thanks to Ilmari Karonen).

{localtime=~/c 25/?say"It's Christmas":redo}

Answer 8

Javascript, 51 chars

It's a CPU killer:

while(!/c 25/.test(Date()));alert("It's Christmas")

Answer 9

R (47)

while(!grepl("c 25",date())){};"It's Christmas"

Answer 10

I wanted to do this without parsing strings. Subsequently, there's a lot of magic numbers in my code.

I did some approximation to account for leap years. No one said that it had to print it out right on 00:00:00, Dec. 25!

Perl, 80 69 57 characters

{(time-30931200)%31557600<86399?die"It's Christmas":redo}

Edited for more concise looping!

Answer 11

Python, 66 68

import time
while'c 25'not in time.ctime():1
print"It's Christmas"

Answer 12

TI-BASIC, 42 38

Repeat 769=sum(getDate²,2
End
"It's Christmas

Expects the date format to be YYYY/MM/DD.

getDate creates a three-element list {year,month,day}; only on Christmas is month^2 + day^2 equal to 769.

23 bytes are used for the string because lowercase letters are two bytes each, except for i which is displayed as the imaginary unit token.

Answer 13

Batch file, 68 chars

:l
@date/t|findstr/c:"-12-25">nul&&echo It's Christmas&&exit
@goto l

Not usable interactively, as it kills the session. Solving that would require 5 more characters.

Also locale-sensitive. This works on my locale which uses ISO 8601 date format.

But hey, it's a batch file (by most not even regarded as a programming language). And shorter than Javascript (and on par with Python).

Answer 14

Groovy, 55

while(!new Date()==~/.*c 25.*/);
println"It's Christmas"

Think it works, but still waiting for output.

Answer 15

(pdf)eTeX - 180 chars only December 1-25.

\lccode`m`~\let\e\expandafter\def~{\ifdim900pt<\pdfelapsedtime
sp\pdfresettimer\else\e~\fi}\lowercase\e{\e\scantokens\e
{\romannumeral\numexpr (25 - \day)*96000}}It's Christmas!\bye

TeX only has a way to access the date when the program starts, and the time elapsed since the start, capped at 32768 seconds, so I need to compute the number of seconds to wait, and for each second do a loop which waits for the elapsed time to reach 1s and reset the time. (Precisely, I'm doing blocks of 900 seconds.)

Working for any month requires more work: 355 chars.

\lccode`m=`~\let\o\or\let\y\year\let\n\numexpr\let\e\expandafter
\def\b#1{\ifnum#1=\n(#1/4)*4\relax+1\fi}\def~{\ifdim
900pt<\pdfelapsedtime sp\pdfresettimer\else\e~\fi}\lowercase
\e{\e\scantokens\e{\romannumeral\n(25-\day+\ifcase\month\o334\b\y
\o303\b\y\o275\o244\o214\o183\o153\o122\o91\o61\o30\o0\ifnum25<\day
365\b{\n\y+1}\fi\fi)*96000}}It's Christmas!\bye

Answer 16

MySQL, 180 chars

Because what are you using your database engine for, anyway?

DELIMITER $$
CREATE FUNCTION c() RETURNS CHAR(14) BEGIN a: LOOP IF DAY(NOW())=25 && MONTH(NOW())=12 THEN RETURN 'It\'s Christmas'; END IF; END LOOP a; END$$
DELIMITER ;
SELECT c();

Not very competitive lengthwise, but hey, it's doable!

Answer 17

Ruby, 53

until Time.now.to_s=~/c 25/
end
puts"It's Christmas!"

Answer 18

PHP, 40 bytes

<?while(date(dm)-1225);?>It´s Christmas;

Loop until 25th of December; then exit to plain mode and print.

Run with default settings (don´t display notices).

Answer 19

8086 machine code, 33 bytes

00000000  b4 2a cd 21 81 fa 19 0c  75 f6 b4 09 ba 12 01 cd  |.*.!....u.......|
00000010  21 c3 49 74 27 73 20 43  68 72 69 73 74 6d 61 73  |!.It's Christmas|
00000020  24                                                |$|
00000021

Answer 20

Forth (gforth), 84 bytes

: f begin time&date drop 12 = 0<> swap 25 = 0<> and until s" It's Christmas!" type ;

Try it online!

Yet another stack language. Somehow not the longest answer.

The time&date word is very convenient here.

A stack overflow happens since time&date values are left on stack every iteration.

Answer 21

Javascript, 93 89 78 77 chars

function x(){Date().match("c 25")?alert("It's Christmas"):setTimeout(x,1)}x()

Answer 22

D, 130

import std.datetime,std.stdio;
main(){
do{
auto t = Clock.currTime();
}while(t.month!=12||t.day!=25);
writeln("It's Christmas");
}

Answer 23

Q, 63 chars

system"t 1000";.z.ts:{$["12.25"~-5#-3!.z.d;1"It's Christmas";]}

will work for christmas day on every year

Answer 24

SQL*Plus + PL/SQL - 100

EXEC LOOP EXIT WHEN TO_CHAR(SYSDATE,'DDMM')='2512';END LOOP;DBMS_OUTPUT.put_line('It''s Christmas');

• Assuming SERVEROUTPUT ON
• Shorter then the MySql solution (eat that, MySql!)
• Too late for last year, but in time for this year
• Tried DBMS_OUTPUT.put instead of DBMS_OUTPUT.put_line but that doesn't print anything.

Answer 25

C# (126)

using System;class P{static void Main(){while(DateTime.Now.Date.ToString("Md")!="1225");Console.WriteLine("It's Christmas");}}

Nicer for your battery:

C# (163)

using s=System;class P{static void Main(){s.Threading.Thread.Sleep(s.DateTime.ParseExact("1225","Md",null)-s.DateTime.Now);s.Console.WriteLine("It's Christmas");}}

edit

The second ("nicer for your battery") version does have a bit of an issue dec. 26th to dec. 31st I just thought of :P

Both versions can probably be shortened a bit more.

Answer 26

VBA, 58 Bytes

Anonymous VBE immediates window function that takes no input and runs until it's Christmas day, at which time it outputs It's Christmas to the VBE immediates window.

While Left(Now,5)<>"12/25":DoEvents:Wend:?"It's Christmas"

Answer 27

SmileBASIC, 49 47 bytes

DTREAD OUT,M,D?"It's Christmas"*(M/D==.48)EXEC.

month/day will be 0.48 on December 25th.

Answer 28

05AB1E, ²⁸ 21 bytes

[že25Qžf12Q&#}”It'sŒÎ

Try it online!

Noncompeting, I suppose(Beats the other non-competing answer, ha).

My first 05AB1E answer.

-7 bytes from ovs.

Explanation

[že25Qžf12Q&#”It'sŒÎ
[                            start an infinite loop
 že                          push current day
   25                        25
     Q                       are they equal?
      žf                     push current month
        12                   12
          Q                  are they equal?
           &                 logical and
            #                break if both conditions are true
             ”It'sŒÎ         push "It's Christmas"
                             implicit output

Answer 29

Japt, 27 bytes

Ks f"c 25" ?`It's CËItµs`:P

To test against today's date : Replace c 25 with this month's last letter (shorthand) + space + day of the month. Feb 02 == b 02

Try it online!

Answer 30

Thunno 2, 23 bytes

(kNkM,¿⁺P¿Q)’It's ñẈmas

Try it online!

Explanation

(kNkM,¿⁺P¿Q)’It's ñẈmas  '# Full program
(          )              # Loop until this returns false:
 kNkM,                    #   Push [current month, current day]
      ¿⁺P¿Q               #   Not equal to [12, 25]
            ’It's ñẈmas  '# Push "It's Christmas"
                          # Implicit output