How to Understand Epoch & Unix Timestamp | Epoch Converter

epoch-unix-timestamp

epoch-unix-timestamp

What is epoch time?

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 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())
R as.numeric(Sys.time())
Erlang calendar:datetime_to_gregorian_seconds(calendar:now_to_universal_time( now()))-719528*24*3600.
MySQL SELECT unix_timestamp(now()) More info (+ negative epochs)
PostgreSQL SELECT extract(epoch FROM now());
Oracle PL/SQL SELECT (SYSDATE – TO_DATE(’01/01/1970 00:00:00′, ‘MM-DD-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.
Tcl/Tk clock seconds
Unix/Linux Shell date +%s
PowerShell Get-Date -UFormat “%s” Produces: 1279152364.63599
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 the Perl Epoch routines
PHP mktime(hour, minute, second, month, day, year) More info
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 (“MM/dd/yyyy HH:mm:ss”).parse(“01/01/1970 01:00:00”).getTime();
VBScript/ASP DateDiff(“s”, “01/01/1970 00:00:00”, time field) More info
C Use the C Epoch Converter routines
R as.numeric(as.POSIXct(“MM/dd/yyyy HH:mm:ss”, origin=”1970-01-01″))
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 Shell 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 the Perl Epoch routines
PHP date(output format, epoch); Output format example: ‘r’ = RFC 2822 date More info
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. More info
Java String date = new java.text.SimpleDateFormat(“MM/dd/yyyy HH:mm:ss”).format(new java.util.Date (epoch*1000));
VBScript/ASP DateAdd(“s”, epoch, “01/01/1970 00:00:00”) More info
C Use the C Epoch Converter routines
R as.POSIXct(epoch, origin=”1970-01-01″)
MySQL from_unixtime(epoch, optional output format) The default output format is YYY-MM-DD HH:MM:SS more …
PostgreSQL PostgreSQL version 8.1 and higher: SELECT to_timestamp(epoch); More info Older versions: SELECT TIMESTAMP WITH TIME ZONE ‘epoch’ + epoch * INTERVAL ‘1 second’;
Oracle PL/SQL SELECT to_date(’01-JAN-1970′,’dd-mon-yyyy’)+(1326357743/60/60/24) from dual
Replace 1326357743 with epoch.
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 time zones: =((A1 +/- time zone adjustment) / 86400) + 25569.
Crystal Reports DateAdd(“s”, {EpochTimeStampField}-14400, #1/1/1970 00:00:00#) -14400 used for Eastern Standard Time. See Time Zones.
JavaScript Use the JavaScript Date object
Tcl/Tk clock format 1325376000 More info
Unix/Linux Shell date -d @1190000000 Replace 1190000000 with your epoch, needs recent version of ‘date’. Replace ‘-d’ with ‘-ud’ for GMT/UTC time.
PowerShell Function get-epochDate ($epochDate) { [timezone]::CurrentTimeZone.ToLocalTime(([datetime]’1/1/1970′).AddSeconds($epochDate)) }, then use: get-epochDate 1279152364. Works for Windows PowerShell v1 and v2
Other OS’s Command line: perl -e “print scalar(localtime(epoch))” (If Perl is installed) Replace ‘localtime’ with ‘gmtime’ for GMT/UTC time.

Reference

http://www.epochconverter.com/