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

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 2

Bash, 39

For those who just can't wait:

sudo date 12250000
echo It\'s Christmas

This follows all of the rules, especially the first one.

Answer 3

Unix, 39 bytes

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

With help from Dennis, thanks for that.

Answer 4

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 5

Python (36 chars)

In the spirit of abusing the rules:

• Definitely prints "It's Christmas" on Christmas

• If it is not Christmas, pass the time by printing "It's Christmas"

  while True:
      print "It's Christmas"
  

Answer 6

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 7

Mathematica, 47

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

Answer 8

R (47)

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

Answer 9

Perl, 44 45

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

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

Answer 10

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 11

Javascript, 51 chars

It's a CPU killer:

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

Answer 12

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 13

Python, 66 68

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

Answer 14

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 15

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 16

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 17

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 18

Groovy, 55

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

Think it works, but still waiting for output.

Answer 19

Ruby, 53

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

Answer 20

(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 21

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 22

Japt, 27 bytes (non-competing)

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! Non-competing because Japt is far newer than this challenge.

Answer 23

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 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

Javascript, 93 89 78 77 chars

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

Answer 27

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 28

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 29

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 30

PHP - 49 Characters

I got this quite short, so yeah.

<?while(date("dm")!="2512");echo"It's Christmas";

EDIT: Whoops, I printed something else than It's Christmas x3

Answer 31

Rebol (53 chars)

wait difference 25-Dec-14 now
print "It's Christmas"

Of course the above will only wait till Xmas 2014 :)

Here's a version that will wait for next Xmas day:

next-xmas: does [
    d: now
    make date! reduce [25 12 either all [d/month = 12 d/day > 25][d/year + 1][d/year]]
]

wait difference next-xmas now
print "It's Christmas"

Answer 32

Befunge-98 (36 chars)

Requires a Unicode-capable interpreter (' is used for a literal 65536 and 'ఙ for 3097):

aa+y'%'ఙ-!#v_
s Christmas"<@,kd"It'

Explanation:

• Use y with an argument of 20 to get the date field (aa+y)
• Mask off the month & day portion by reducing mod-65536 ('%)
• Subtract 3097 (= month * 256 + day) ('ఙ-)
• If zero, print the string (abuses edge wrapping)
• Otherwise repeat

Answer 33

J, 54

'It''s Christmas'[(-^:(3 :'-.12 25-:1 2{6!:0''''')^:_)1

Answer 34

bash-n-date: 69 chars:

sleep $(($(date -d"12/25" +%s)-$(date +%s))) && echo "It's X-Ray    "

But it will fail on Dec. 26th to Dec. 31th.

Answer 35

Q (60)

 system"t 1000";.z.ts:{if[.z.d~2012.12.25;1"It’s Christmas"]}

Answer 36

Groovy - 88

new Timer().schedule({print"It's Christmas"}as TimerTask,Date.parse("yyddMM","112512"))