What is epoch time?

http://www.epochconverter.com/

unix 时间转换器

The  Unix epoch   (or  Unix time   or  POSIX time   or  Unix timestamp ) is the number of seconds that have elapsed since January 1, 1970 (midnight UTC/GMT), not counting leap seconds (in ISO 8601: 1970-01-01T00:00:00Z). Literally speaking the epoch is Unix time 0 (midnight 1-1-1970), but 'epoch' is often used as a synonym for 'Unix time'. Many Unix systems store epoch dates as a signed 32-bit integer, which might cause problems on January 19, 2038 (known as the Year 2038 problem or Y2038). 

Human readable time	Seconds
1 minute	60 seconds
1 hour	3600 seconds
1 day	86400 seconds
1 week	604800 seconds
1 month (30.44 days)	2629743 seconds
1 year (365.24 days)	31556926 seconds

 

 How to get the current epoch time in ...

Perl	time
PHP	time()
Ruby	Time.now   (or  Time.new ). To display the epoch:  Time.now.to_i
Python	import time   first, then  time.time()
Java	long epoch = System.currentTimeMillis()/1000;
Microsoft .NET C#	epoch = (DateTime.Now.ToUniversalTime().Ticks - 621355968000000000) / 10000000;
VBScript/ASP	DateDiff("s", "01/01/1970 00:00:00", Now())
Erlang	calendar:datetime_to_gregorian_seconds(calendar:now_to_universal_time( now()))-719528*24*3600.
MySQL	SELECT unix_timestamp(now())
PostgreSQL	SELECT extract(epoch FROM now());
Oracle PL/SQL	SELECT (SYSDATE - TO_DATE('01-01-1970 00:00:00', 'DD-MM-YYYY HH24:MI:SS')) *  24 * 60 * 60 FROM DUAL
SQL Server	SELECT DATEDIFF(s, '1970-01-01 00:00:00', GETUTCDATE())
JavaScript	Math.round(new Date().getTime()/1000.0)   getTime() returns time in milliseconds.
Unix/Linux	date +%s
Other OS's	Command line:  perl -e "print time"   (If Perl is installed on your system)

 Convert from human readable date to epoch

Perl	Use these  Perl Epoch routines
PHP	mktime(hour ,  minute ,  second ,  month ,  day ,  year )
Ruby	Time.local(year ,  month ,  day ,  hour ,  minute ,  second ,  usec   )   (or  Time.gm   for GMT/UTC input). To display add  .to_i
Python	import time   first, then  int(time.mktime(time.strptime('2000-01-01 12:34:00', '%Y-%m-%d %H:%M:%S'))) - time.timezone
Java	long epoch = new java.text.SimpleDateFormat ("dd/MM/yyyy HH:mm:ss").parse("01/01/1970 01:00:00");
VBScript/ASP	DateDiff("s", "01/01/1970 00:00:00",  time field )
MySQL	SELECT unix_timestamp(time )   Time format: YYYY-MM-DD HH:MM:SS or YYMMDD or YYYYMMDD More on using Epoch timestamps with MySQL
PostgreSQL	SELECT extract(epoch FROM date('2000-01-01 12:34')); With timestamp:  SELECT EXTRACT(EPOCH FROM TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-08'); With interval:  SELECT EXTRACT(EPOCH FROM INTERVAL '5 days 3 hours');
SQL Server	SELECT DATEDIFF(s, '1970-01-01 00:00:00',  time field )
JavaScript	use the  JavaScript Date object
Unix/Linux	date +%s -d"Jan 1, 1980 00:00:01"   Replace '-d' with '-ud' to input in GMT/UTC time.

 Convert from epoch to human readable date

Perl	Use these  Perl Epoch routines
PHP	date(output format ,  epoch );   Output format example: 'r' = RFC 2822 date
Ruby	Time.at(epoch )
Python	import time   first, then  time.strftime("%a, %d %b %Y %H:%M:%S +0000", time.localtime(epoch ))   Replace time.localtime with time.gmtime for GMT time.
Java	String date = new java.text.SimpleDateFormat("dd/MM/yyyy HH:mm:ss").format(new java.util.Date (epoch *1000));
VBScript/ASP	DateAdd("s",  epoch , "01/01/1970 00:00:00")
PostgreSQL	SELECT TIMESTAMP WITH TIME ZONE 'epoch' +  epoch   * INTERVAL '1 second';
MySQL	from_unixtime(epoch ,  optional output format )   The default output format is YYY-MM-DD HH:MM:SS  more ...
SQL Server	DATEADD(s,  epoch , '1970-01-01 00:00:00')
Microsoft Excel	=(A1 / 86400) + 25569   Format the result cell for date/time, the result will be in GMT time (A1 is the cell with the epoch number). For other timezones: =((A1 +/- timezone adjustment) / 86400) + 25569.
JavaScript	use the  JavaScript Date object
Unix/Linux	date -d @1190000000   Replace 1190000000 with your epoch, needs recent version of 'date'. Replace '-d' with '-ud' for GMT/UTC time.
Other OS's	Command line:  perl -e "print scalar(localtime(epoch ))"   (If Perl is installed) Replace 'localtime' with 'gmtime' for GMT/UTC time.