How long ago was this?

Question

The Rules

• Each submission must be a full program.

• The program must take input as two comma-separated dates in the form YYYY-MM-DD, and print the number of days that has passed since the second date to STDOUT as if today was the first date (if the second date would be in the future, output a negative number) plus an optional trailing newline, and nothing else. Assume both dates are in the Gregorian calendar.

• The program must not write anything to STDERR.

  Note that there must be an interpreter so the submission can be tested.

• Submissions are scored in bytes, in an appropriate (pre-existing) encoding, usually (but not necessarily) UTF-8. Some languages, like Folders, are a bit tricky to score - if in doubt, please ask on Meta.

• This is code-golf, so shortest code wins

Examples

Input:

2015-12-03,2015-12-01

Output:

2

Input:

2015-12-03,2014-12-01

Output:

367

Input:

2015-12-03,2013-12-03

Output:

730

Answer 1

Bash + GNU utilities, 37

tr , \\n|date -f- +%s|dc -e??-86400/p

tr replaces the comma with a newline. date reads the newline separated dates and outputs the number of seconds since the Unix epoch that the passed-in date represents. These numbers are then put on the dc stack. Then its a simple matter of subtraction and divide by (24*60*60). In this case, dc stack-based RPN arithmetic evaluation is better than bc or bash $( ), mostly because the subraction-before-division needs no parentheses.

Input via STDIN:

$ echo 2015-12-3,2015-12-1 | ./longago.sh
2
$ echo 2015-12-3,2014-12-1 | ./longago.sh
367
$ echo 2015-12-3,2013-12-3 | ./longago.sh
730
$ 

Answer 2

Julia, 67 bytes

print(Int(-diff(map(i->Date(i,"y-m-d"),split(readline(),",")))[1]))

Ungolfed:

# Read a line from STDIN
r = readline()

# Split it into two character dates
s = split(r, ",")

# Convert each to a Date object
d = map(i -> Date(i, "y-m-d"), s)

# Compute the difference in dates (first-second)
f = diff(d)[1]

# Convert the Base.Date.Day object to an integer
# Negate to get second-first
i = Int(-f)

# Print to STDOUT
print(i)

Answer 3

Scala, 166 139 120 116 92 bytes

print(args(0).replace('-','/').split(",").map(java.util.Date.parse(_)/86400000).reduce(_-_))

Usage: scala [source filename].scala [date1],[date2]

Note: The third version (120 bytes) and on uses a deprecated API. It still compiles and works fine. Note2: Thanks to the commenters below for the great advice!

Answer 4

Ruby, 69 66 65 57 55 bytes

a=->l{Time.gm *$F[l,3]};p (a[0]-a[3]).div 86400

47 bytes + 8 bytes for command line option. Thanks to Dane Anderson, saved 2 bytes.

57 bytes

p (Time.gm(*$F[0,3])-Time.gm(*$F[3,3])).div 86400

49 bytes code + 8 bytes for command line option. Saved 8 bytes with manatwork's suggestion.

65 bytes

a,b=gets.split(?,).map{|i|Time.gm *i.split(?-)};p (a-b).div 86400

66 bytes

a,b=gets.split(?,).map{|i|Time.new *i.split(?-)};p (a-b).div 86400

69 bytes

a,b=gets.split(',').map{|i|Time.new *i.split('-')};p (a-b).to_i/86400

Test it online

Ungolfed

a = -> l {
  Time.gm *$F[l,3]       # Anonymous method to parse time
}
p (a[0]-a[3]).div 86400  # Subtracts two times and divides by 24*60*60

Usage:

ruby -naF[,-] -e 'a=->l{Time.gm *$F[l,3]};p (a[0]-a[3]).div 86400' <<< '2015-12-3,2013-12-3'

=> 730

Answer 5

Japt, 41 bytes

A=K$.parse)(($B=Uq',  g0)-$A($Bg1))/864e5

So far this is the best I can get it as all the variables and $ and parenthesis really kill the byte count.

Try it online

Explanation

             // Implicit: U is set to input
A=K$.parse)  // Set variable A to date parsing function
(($B=Uq',    // Set B to input split by ,
  g0)        // Get the first date and parse
-            // Subtract...
$A(          // Parse this date...
   $Bg1      // Get's second date
))/864e5     // Divides by 86,400,000

Answer 6

MATLAB, 41 31 bytes

disp(-diff(datenum(input(''))))
{'2015-12-03', '2014-12-22'}
   346  

Input must be a comma-separated cell array. datenum converts the input cell into a 2x1 numeric array with the time stamp. diff takes the difference between the two.

---

Old solution, 41 bytes:

disp(-diff(datenum(strsplit(input('')))))

Input must be a comma-separated string:

disp(-diff(datenum(strsplit(input('')))))
'2015-12-03, 2014-12-22'
   346

The curious ways of programming. This works because of MATLAB's implicit casting between datatypes.

The output from strsplit(input('')) is a cell of strings. You cannot use diff on a cell, but fortunately, datenum works, and it actually casts the cell input back to a 2x1 numeric array, making diff possible to use.

You can specify a whole lot of delimiters in strsplit, but comma is the default one. Also, the default input to datenum is on the format yyyy-mm-dd. For those reasons, a lot of specifications such as: datenum(s,'yyyy-mm-dd') are avoided, saving a whole lot of bytes.

For the record, this would be 21 bytes if I could use a function:

@(s)-diff(datenum(s))

Answer 7

Javascript ES6, 63 bytes

Tested in chrome.

alert(((p=Date.parse)((a=prompt().split`,`)[0])-p(a[1]))/864e5)

Answer 8

PHP, 63 64 77 bytes

Found that the classic approach is shorter than the OOP one:

$x=fgetcsv(STDIN);$s=strtotime;echo($s($x[0])-$s($x[1]))/86400;

Reads the comma separated string from STDIN.

---

The straight forward OOP way (77 bytes):

$x=fgetcsv(STDIN);echo(new DateTime($x[0]))->diff(new DateTime($x[1]))->days;

---

Edits

• Saved 13 bytes by using strtotime instead of DateTime.
• Saved 1 byte by storing strtotime in a variable. Thanks to Blackhole.

Answer 9

Excel, 25 bytes

=LEFT(A1,10)-RIGHT(A1,10)

Excel automatically handles the strings as dates.

Answer 10

TeaScript, 24 bytes

((a=D.parse)×-a(y©/864e5

Uses Date.parse to parse the date, then get's the difference and divides.

Try it online

Explanation && Ungolfed

((a=D.parse)(x)-a(y))/864e5

               // Implicit: x is first date
               // y is second date
(
 (a=D.parse)   // Assign Date.parse to 'a'
 (x)           // Run Date.parse with first date
 -a(y)         // Subtract Date.parse run with second date
)/864e5        // Divide by 86,400,000

Answer 11

VBA, 69 bytes

Function x(s)
g=Split(s, ",")
x=CDate(g(0))-CDate(g(1))
End Function

Answer 12

psql, 75 bytes

(74 characters code + 1 character command line option)

\prompt i
select split_part(:'i',',',1)::date-split_part(:'i',',',2)::date

psql is PostgreSQL's interactive terminal. To respect the “Each submission must be a full program.” rule, the code reads the input itself.

Sample run:

bash-4.3$ psql -tf how-long-was-this.sql <<< '2015-12-3,2013-12-3'
      730

Answer 13

Python 2, 109 113 bytes

import datetime as d 
j=[d.date(*[int(k) for k in g.split('-')]) for g in raw_input().split(',')]
print j[0]-j[1]

Answer 14

MATL, 5 bytes

iPYOd

This is the same as StewieGriffin's answer, except I used flip then diff rather than diff then negating the result.

Full explanation, with corresponding Matlab functions:

i   %// input(''), get input
P   %// flip, flips the array
YO  %// datenum, converts date string into an integer
d   %// diff, finds the difference between dates

Answer 15

PowerShell v2+, 50 44 Bytes

$a,$b=$args-split','|%{date $_};($a-$b).Days

Takes input argument as a string, splits it on the comma, then pipes the array via a built-in alias date short for Get-Date to convert our strings into .NET datetime format. Those two dates then get stored simultaneously into $a and $b. We then use an overloaded-subtraction-operator to subtract the second from the first, and output the .Days thereof.

Golfed 6 bytes thanks to TessellatingHeckler.

Technically non-competing, as it doesn't have an online interpreter available, since the FOSS implementation of PowerShell, Pash, is around PowerShell v0.5. It doesn't support -split yet, let alone the complex .NET date functionality.

Answer 16

Japt, 13 bytes

£ÐXÃr- zHÑ7e5

Try it

Answer 17

JavaScript, 58 53 bytes thanks to @targumon!

n=>(new Date((a=n.split`,`)[0])-new Date(a[1]))/864e5

Older version:

n=>(new Date((a=n.split(','))[0])-new Date(a[1]))/86400000

My submissions seem to have a reputation of being boring.

Answer 18

Jolf, 33 bytes

Only works in Chrome. Noncompeting, since language updates postdate question. I'll add a more thorough explanation later.

$S=$viGi', mDN~DH r}/m4SmeP"864"5

“Explanation”

$S=$viGi', mDN~DH r}
$S=$                 sets S equal to
    viGi',           take string input and reassign it to the comma-split input
           mD      } map with this function 
             N~DH r  return the time of the date of H (element)

/m4SmeP"864"5
/             divide
 m4S           subtraction applied to S (S[0] - S[1])
    meP"864"5  and 864 * 10 ^ 5 (thanks to Super Jedi for his nice constant)
              implicit output

Answer 19

MATLAB, 59 bytes

s=strsplit(input(''),',');disp(datenum(s{1})-datenum(s{2}))

Very straightforward approach: input has to be given as a string from the command window. The input string is then split and the number of days between the dates (and nothing else) is calculated from the serial date numbers. I'm quite sure there is a way to avoid the need for calling datenum twice though...

Answer 20

T-SQL + SQLCMD, 51 bytes

PRINT DATEDIFF(D,RIGHT('$(i)',10),LEFT('$(i)',10))

Tested with SQL Server 2008R2. The $(i) is replaced with the input provided as a command line argument.

Sample run:

sqlcmd -i script.sql -v i="2015-12-08,2016-01-01"
-24

Answer 21

Mathematica, 61 bytes

Print@First[#-#2&@@DateObject/@InputString[]~StringSplit~","]

Basic date subtraction.

Answer 22

Perl, 91 86 + 2 for np flags, 88 bytes

use Date::Calc qw(Delta_Days);($a,$b)=split(/,/);$_=Delta_Days(split(/-/,$b),split(/-/,$a))

use Date::Parse;$_=str2time((split(/,/,$_))[0])-str2time((split(/,/,$_))[1]);$_/=86400

Example

$ echo 2015-12-3,2015-12-1 | perl -npe 'use Date::Parse;$_=str2time((split(/,/,$_))[0])-str2time((split(/,/,$_))[1]);$_/=86400'
2

Answer 23

jq, 50 bytes

(49 characters code + 1 character command line option)

./","|map(.+"T0:0:0Z"|fromdate)|(.[0]-.[1])/86400

Sample run:

bash-4.3$ ~/bin/jq -R './","|map(.+"T0:0:0Z"|fromdate)|(.[0]-.[1])/86400' <<< '2015-12-3,2013-12-3'
730

On-line test (Passing -R through URL is not supported – so input passed as string "2015-12-3,2013-12-3".)

Answer 24

Mathematica, 56 bytes

Print@#&@@-DateDifference@@InputString[]~StringSplit~","

Most (all?) date functions will try to parse string inputs into dates automatically.

Answer 25

C# .NET, 148 bytes

using System;class P{static void Main(string[]a){Console.Write((DateTime.Parse(a[0].Substring(11,10))-DateTime.Parse(a[0].Substring(0,10))).Days);}}

Try Online

Answer 26

C (gcc), 225 199 bytes

-25 bytes thanks to ceilingcat! Replacing an array of numbers with a string of wide-characters is some proper black-magic

-1 byte by adding an additional character to the start of the string, allowing for indexing with [m] instead of [m-1]

a,b,d,e,f;i(m,y){return(a=y-1)*365+a/4-a/100+a/400+L"\0\37;Zx\x97µÔóđİŎ"[m]+(m>1&(y%100*!(y%4)||y%400<1));}main(c){scanf("%d-%d-%d,%d-%d-%d",&a,&b,&c,&d,&e,&f);printf("%d",i(b,a)-i(e,d)+c-f);}

Try it online!

Perhaps the code could be shortened by using <time.h>, but not using it makes for a fun challenge. The difference between dates is calculated using a golfed version of this code.

Un-golfed:

a,b,d,e,f;
i(m,y){
    return(a=y-1)*365 /*Num days in y-1 years*/
        +a/4-a/100+a/400 /*Add previous years' leap days*/
        +L" \0\37;Zx\x97µÔóđİŎ"[m] /*Add days this year until month*/
        +(m>1&(y%100*!(y%4)||y%400<1)); /*Add this year's leap day*/
}
main(c){
    scanf("%d-%d-%d,%d-%d-%d",&a,&b,&c,&d,&e,&f);
    printf("%d",i(b,a)-i(e,d)+c-f);
}