Show the epoch

Show the epoch
You are encouraged to solve this task according to the task description, using any language you may know.

Choose popular date libraries used by your language and show the epoch those libraries use. A demonstration is preferable (e.g. setting the internal representation of the date to 0 ms/ns/etc., or another way that will still show the epoch even if it is changed behind the scenes by the implementers), but text from (with links to) documentation is also acceptable where a demonstration is impossible/impractical. For consistency's sake, show the date in UTC time where possible.

See also: Date format

Ada

In Ada, time is a private type and is implementation defined, for instance, on 64 bit GNAT, time is represented internally as nanoseconds relative to Jan 1, 2150.

However, conversion from unix epoch seconds is also supported and shown below.

with Ada.Text_IO; use Ada.Text_IO;
with Ada.Calendar; use Ada.Calendar;
with Ada.Calendar.Formatting; use Ada.Calendar.Formatting;
with Ada.Calendar.Conversions; use Ada.Calendar.Conversions;
procedure ShowEpoch is
   etime : Time := To_Ada_Time (0);
begin
   Put_Line (Image (Date => etime));
end ShowEpoch;

Output:

1970-01-01 00:00:00

AWK

 
# syntax: GAWK -f SHOW_THE_EPOCH.AWK
# requires GNU Awk 4.0.1 or later
BEGIN {
    print(strftime("%Y-%m-%d %H:%M:%S",0,1))
    exit(0)
}
 

output:

1970-01-01 00:00:00

BBC BASIC

Works with: BBC BASIC for Windows

      INSTALL @lib$+"DATELIB"
      PRINT FN_date$(0, "dd-MMM-yyyy")

Output:

17-Nov-1858

C

#include <time.h>
#include <stdio.h>
 
int main() {
    time_t t = 0;
    printf("%s", asctime(gmtime(&t)));
    return 0;
}

Output:

Thu Jan  1 00:00:00 1970

Windows

FileTime, from the Win32 API, uses a different epoch.

Library: Win32

#include <windows.h>
#include <stdio.h>
#include <wchar.h>
 
int
main()
{
	FILETIME ft = {dwLowDateTime: 0, dwHighDateTime: 0};  /* Epoch */
	SYSTEMTIME st;
	wchar_t date[80], time[80];
 
	/*
	 * Convert FILETIME (which counts 100-nanosecond intervals since
	 * the epoch) to SYSTEMTIME (which has year, month, and so on).
	 *
	 * The time is in UTC, because we never call
	 * SystemTimeToTzSpecificLocalTime() to convert it to local time.
	 */
	FileTimeToSystemTime(&ft, &st);
 
	/*
	 * Format SYSTEMTIME as a string.
	 */
	if (GetDateFormatW(LOCALE_USER_DEFAULT, DATE_LONGDATE, &st, NULL,
	    date, sizeof date / sizeof date[0]) == 0 ||
	    GetTimeFormatW(LOCALE_USER_DEFAULT, 0, &st, NULL,
	    time, sizeof time / sizeof time[0]) == 0) {
		fwprintf(stderr, L"Error!\n");
		return 1;
	}
 
	wprintf(L"FileTime epoch is %ls, at %ls (UTC).\n", date, time);
	return 0;
}

Output:

FileTime epoch is Monday, January 01, 1601, at 12:00:00 AM (UTC).

C#

using System;
 
class Program
{
    static void Main()
    {
        Console.WriteLine(new DateTime());
    }
}

Output:

1-1-0001 0:00:00

C++

Works with: C++11

Works with: gcc version 4.5.3

Doesn't work with MSVC 10 SP1

#include <iostream>
#include <chrono>
#include <ctime>
int main()
{
    std::chrono::system_clock::time_point epoch;
    std::time_t t = std::chrono::system_clock::to_time_t(epoch);
    std::cout << std::asctime(std::gmtime(&t)) << '\n';
    return 0;
}

Output:

Thu Jan  1 00:00:00 1970

Library: boost

#include <iostream>
#include <boost/date_time.hpp>
int main()
{
    std::cout << boost::posix_time::ptime( boost::posix_time::min_date_time ) << '\n';
    return 0;
}

Output:

1400-Jan-01 00:00:00

Common Lisp

(multiple-value-bind (second minute hour day month year) (decode-universal-time 0 0)
 	  (format t "~4,'0D-~2,'0D-~2,'0D ~2,'0D:~2,'0D:~2,'0D" year month day hour minute second))

Output:

1900-01-01 00:00:00

D

The Date struct of the standard library module "std.datetime" represents a date in the Proleptic Gregorian Calendar ranging from 32,768 B.C. to 32,767 A.D.

Dart

main() {
  print(new Date.fromEpoch(0,new TimeZone.utc()));
}

Output:

1970-01-01 00:00:00.000Z

Delphi

program ShowEpoch;
 
{$APPTYPE CONSOLE}
 
uses SysUtils;
 
begin
  Writeln(FormatDateTime('yyyy-mm-dd hh:nn:ss.zzz', 0));
end.

Output:

1899-12-30 00:00:00.000

Factor

 
IN: USE: calendar calendar.format
IN: 0 micros>timestamp timestamp>ymdhms .
"1970-01-01 00:00:00"
 

Forth

Works with: 4tH version 3.61.3

include lib/longjday.4th
0 posix>jday .longjday  cr

Output:

Thursday, January 1, 1970

Go

package main
import ("fmt"; "time")
 
func main() {
    fmt.Println(time.Time{})
}

Output:

This is UNIX format. The 1 on the end is the full year, not two or four digit year.

Mon Jan  1 00:00:00 +0000 UTC 1

Groovy

Groovy uses the UNIX epoch.

def date = new Date(0)
def format = new java.text.SimpleDateFormat('yyyy-MM-dd\'T\'HH:mm:ss.SSSZ')
format.timeZone = TimeZone.getTimeZone('UTC')
println (format.format(date))

Output:

1970-01-01T00:00:00.000+0000

Haskell

Old time library

The ClockTime type is abstract in Haskell 98, but is defined in GHC.

Works with: GHC

import System.Time
 
main = putStrLn $ calendarTimeToString $ toUTCTime $ TOD 0 0

Output:

Thu Jan  1 00:00:00 UTC 1970

New time library

Works with: GHC

import Data.Time
 
main = print $ UTCTime (ModifiedJulianDay 0) 0

Output:

1858-11-17 00:00:00 UTC

Icon and Unicon

Date and Time can be accessed via a number of keywords and functions

• The following are available in both Icon and Unicon
  • &clock, &date, &dateline, and &time deal with current times and dates
• The following are specific to Unicon
  • &now provides the number of seconds since the epoch, Jan 1, 1970 00:00:00
  • ctime(integer) takes the number of seconds since the epoch and returns the date and time as a string in the local timezone
  • gtime(integer) takes the number of seconds since the epoch and returns the date and time as a string in UTC
  • gettimeofday() returns a record with the current time since the epoch in seconds and microseconds

Library: Icon Programming Library

• datetime routines use a global variable 'DateBaseYear' which defaults to Jan 1, 1970 00:00:00 but can be set if desired.
• The example below uses only a couple of the datetime procedures

link printf,datetime
 
procedure main()
  # Unicon
  now := gettimeofday().sec
  if now = &now then printf("&now and gettimeofday().sec are equal\n") 
  printf("Now (UTC) %s, (local) %s\n",gtime(now),ctime(now))
  printf("Epoch %s\n",gtime(0))
  # Icon and Unicon
  now := DateToSec(&date) + ClockToSec(&clock)
  printf("Now is also %s and %s\n",SecToDate(now),SecToDateLine(now))  
end

Sample Output:

&now and gettimeofday().sec are equal
Now (UTC) Tue Aug 09 10:43:23 2011, (local) Tue Aug 09 06:43:23 2011
Epoch Thu Jan 01 00:00:00 1970
Now is also 2011/08/09 and Tuesday, August 9, 2011  6:43 am

J

J does not have an epoch. J's native representation of date and time is a six element list: year, month, day, hour, minute, second. For example:

   6!:0''
2011 8 8 20 25 44.725

(August 8, 2011, 8:25:44 pm)

That said, the 'dates' library does have an epoch:

   require'dates'
   todate 0
1800 1 1

Java

DateFormat is needed to set the timezone. Printing date alone would show this date in the timezone/locale of the machine that the program is running on. The epoch used in java.util.Date (as well as java.sql.Date, which can be subbed into this example) is actually in GMT, but there isn't a significant difference between that and UTC for lots of applications (documentation for java.util.Date).

import java.text.DateFormat;
import java.util.Date;
import java.util.TimeZone;
 
public class DateTest{
    public static void main(String[] args) {
        Date date = new Date(0);
        DateFormat format = DateFormat.getDateTimeInstance();
        format.setTimeZone(TimeZone.getTimeZone("UTC"));
        System.out.println(format.format(date));
    }
}

Output:

Jan 1, 1970 12:00:00 AM

On my PC I see

01.01.1970 00:00:00

JavaScript

document.write(new Date(0).toUTCString());

Output:

Thu, 01 Jan 1970 00:00:00 GMT

Mathematica

DateString[0]

->Mon 1 Jan 1900 00:00:00

MATLAB / Octave

Matlab and Octave store date/time number in a floating point number counting the days.

d = [0,1,2,3.5,-3.5,1000*365,1000*366,now+[-1,0,1]];
for k=1:length(d)
    printf('day %f\t%s\n',d(k),datestr(d(k),0))
    disp(datevec(d(k)))
end;

Output:

day 0.000000	31-Dec--001 00:00:00
   -1   12   31    0    0    0
day 1.000000	01-Jan-0000 00:00:00
   0   1   1   0   0   0
day 2.000000	02-Jan-0000 00:00:00
   0   1   2   0   0   0
day 3.500000	03-Jan-0000 12:00:00
    0    1    3   12    0    0
day -3.500000	27-Dec--001 12:00:00
   -1   12   27   12    0    0
day 365000.000000	02-May-0999 00:00:00
   999     5     2     0     0     0
day 366000.000000	27-Jan-1002 00:00:00
   1002      1     27      0      0      0
day 734908.972013	09-Feb-2012 23:19:41
   2012.0000      2.0000      9.0000     23.0000     19.0000     41.9633
day 734909.972013	10-Feb-2012 23:19:41
   2012.0000      2.0000     10.0000     23.0000     19.0000     41.9633
day 734910.972013	11-Feb-2012 23:19:41
   2012.0000      2.0000     11.0000     23.0000     19.0000     41.9633

Maxima

timedate(0);
"1900-01-01 10:00:00+10:00"

NetRexx

Translation of: Java

/* NetRexx */
options replace format comments java crossref symbols nobinary
 
import java.text.DateFormat
 
edate = Date(0)
zulu  = DateFormat.getDateTimeInstance()
zulu.setTimeZone(TimeZone.getTimeZone('UTC'))
say zulu.format(edate)
return
 

Output:

Jan 1, 1970 12:00:00 AM

NewLISP

(date 0)
->"Thu Jan 01 01:00:00 1970"

Objective-C

#import <Foundation/Foundation.h>
 
int main(int argc, const char *argv[]) {
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
 
  NSDate *t = [NSDate dateWithTimeIntervalSinceReferenceDate:0];
  NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc] init] autorelease];
  [dateFormatter setTimeZone:[NSTimeZone timeZoneWithName:@"UTC"]];
  [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss ZZ"];
  NSLog(@"%@", [dateFormatter stringFromDate:t]);
 
  [pool release];
  return 0;
}

Log:

2001-01-01 00:00:00 +0000

OCaml

open Unix
 
let months = [| "January"; "February"; "March"; "April"; "May"; "June";
      "July"; "August"; "September"; "October"; "November"; "December" |]
 
let () =
  let t = Unix.gmtime 0.0 in
  Printf.printf "%s %d, %d\n" months.(t.tm_mon) t.tm_mday (1900 + t.tm_year)

Execution:

$ ocaml unix.cma epoch.ml
January 1, 1970

Pascal

This works with Free Pascal:

Program ShowEpoch;
 
uses
  SysUtils;
 
begin
  Writeln(FormatDateTime('yyyy-mm-dd hh:nn:ss.zzz', Now));
  Writeln(FormatDateTime('yyyy-mm-dd hh:nn:ss.zzz', 0));
end.

Output:

:> ./SelfDescribingNumber
2011-12-13 00:57:41.378
1899-12-30 00:00:00.000

Perl

print scalar gmtime 0, "\n";

Output:

Thu Jan  1 00:00:00 1970

Perl 6

say DateTime.new(0)

Output:

1970-01-01T00:00:00Z

PHP

<?php
echo gmdate('r', 0), "\n";
?>

Output:

Thu, 01 Jan 1970 00:00:00 +0000

PicoLisp

The 'date' function in PicoLisp returns a day number, starting first of March of the year zero. Calculated according to the gregorian calendar (despite that that calendar wasn't used in 0 AD yet).

: (date 1)
-> (0 3 1)  # Year zero, March 1st

PL/I

show_epoch: procedure options (main); /* 14 Sept. 2012 */
   put (datetime('DDMmmYYYY'));
   put (time());
end show_epoch;

Result:

14Sep2012               233312540

PowerShell

PowerShell uses .NET's DateTime structure and an integer can simply be casted appropriately:

[datetime] 0

Output:

Monday, January 01, 0001 12:00:00 AM

PureBasic

If OpenConsole()
  PrintN(FormatDate("Y = %yyyy  M = %mm  D = %dd, %hh:%ii:%ss", 0))
 
  Print(#CRLF$ + #CRLF$ + "Press ENTER to exit"): Input()
  CloseConsole()
EndIf

Output:

Y = 1970  M = 01  D = 01, 00:00:00

Python

>>> import time
>>> time.asctime(time.gmtime(0))
'Thu Jan  1 00:00:00 1970'
>>>

R

> epoch <- 0
> class(epoch) <- class(Sys.time())
> format(epoch, "%Y-%m-%d %H:%M:%S %Z")
[1] "1970-01-01 00:00:00 UTC"

Racket

 
#lang racket
(require racket/date)
(date->string (seconds->date 0 #f))
 

Output:

"Thursday, January 1st, 1970"

REXX

The epoch for the REXX language built-in function DATE is January 1st, year 1.

/*REXX program shows the # of days since the epoch for the DATE function*/
 
say '     today is' date()             /*today's is format: mm MON YYYY */
 
days=date('Basedate')                  /*only 1st char of option is used*/
say right(days,35) "days since the REXX base date of January 1st, year 1"
 
say 'and today is:' date(,days,'B')    /*this should be today (still).  */
 
      /*──────── The above statement is only valid for the newer REXXes,*/
      /*──────── older versions don't support the 2nd and 3rd arguments.*/

output

     today is 3 Aug 2012
                             734717 days since the REXX base date of January 1st, year 1
and today is: 3 Aug 2012

Ruby

irb(main):001:0> Time.at(0).utc
=> 1970-01-01 00:00:00 UTC

Run BASIC

eDate$ = date$("01/01/0001")
cDate$ = date$(0) ' 01/01/1901
sDate$ = date$("01/01/1970")

Scala

import java.util.{Date, TimeZone, Locale}
import java.text.DateFormat
 
val df=DateFormat.getDateTimeInstance(DateFormat.LONG, DateFormat.LONG, Locale.ENGLISH)
df.setTimeZone(TimeZone.getTimeZone("UTC"))
println(df.format(new Date(0)))

Output:

January 1, 1970 12:00:00 AM UTC

Seed7

The Seed7 library time.s7i defines the type time, which describes times and dates. For dates the proleptic Gregorian calendar is used (which assumes that the Gregorian calendar was even in effect at dates preceding its official introduction). This convention is used according to ISO 8601, which also defines that positive and negative years exist and that the year preceding 1 is 0. Therefore the epoch is the beginning of the year 0.

$ include "seed7_05.s7i";
  include "time.s7i";
 
const proc: main is func
  begin
    writeln(time.value);
  end func;

Output:

0000-01-01 00:00:00 UTC

Standard ML

- Date.toString (Date.fromTimeUniv Time.zeroTime);
val it = "Thu Jan  1 00:00:00 1970" : string

Tcl

% clock format 0 -gmt 1
Thu Jan 01 00:00:00 GMT 1970

TUSCRIPT

$$ MODE TUSCRIPT
- epoch
number=1
dayofweeknr=DATE (date,day,month,year,number)
epoch=JOIN(year,"-",month,day)
PRINT "epoch: ", epoch," (daynumber ",number,")"
- today's daynumber
dayofweeknr=DATE (today,day,month,year,number)
date=JOIN (year,"-",month,day)
PRINT "today's date: ", date," (daynumber ", number,")"

Output:

epoch: 1-1-1 (daynumber 1)
today's date: 2011-12-14 (daynumber 734487) 

UNIX Shell

The nonstandard option date -r takes seconds from the epoch, and prints date and time. See date(1) manual.

Works with: OpenBSD

$ date -ur 0
Thu Jan  1 00:00:00 UTC 1970

On systems with GNU date, you can do

 
$ TZ=UTC  date --date "$(date +%s) seconds ago"
Thu Jan  1 00:00:00 UTC 1970
 

Visual Basic

Sub Main()
    Debug.Print Format(0, "dd mmm yyyy hh:mm")
End Sub

Output (in debug window):

30 Dec 1899 00:00