NAME¶
DateTime::Format::Epoch - Convert DateTimes to/from epoch seconds
SYNOPSIS¶
use DateTime::Format::Epoch;
my $dt = DateTime->new( year => 1970, month => 1, day => 1 );
my $formatter = DateTime::Format::Epoch->new(
epoch => $dt,
unit => 'seconds',
type => 'int', # or 'float', 'bigint'
skip_leap_secondss => 1,
start_at => 0,
local_epoch => undef,
);
my $dt2 = $formatter->parse_datetime( 1051488000 );
# 2003-04-28T00:00:00
$formatter->format_datetime($dt2);
# 1051488000
DESCRIPTION¶
This module can convert a DateTime object (or any object that can be converted
to a DateTime object) to the number of seconds since a given epoch. It can
also do the reverse.
METHODS¶
- •
- new( ... )
Constructor of the formatter/parser object. It can take the following
parameters: "epoch", "unit", "type",
"skip_leap_seconds", "start_at",
"local_epoch" and "dhms".
The epoch parameter is the only required parameter. It should be a DateTime
object (or at least, it has to be convertible to a DateTime object). This
datetime is the starting point of the day count, and is usually numbered
0. If you want to start at a different value, you can use the start_at
parameter.
The unit parameter can be "seconds", "milliseconds,
"microseconds" or "nanoseconds". The default is
"seconds". If you need any other unit, you must specify the
number of units per second. If you specify a number of units per second
below 1, the unit will be longer than a second. In this way, you can count
days: unit => 1/86_400.
The type parameter specifies the type of the return value. It can be
"int" (returns integer value), "float" (returns
floating point value), or "bigint" (returns Math::BigInt value).
The default is either "int" (if the unit is
"seconds"), or "bigint" (if the unit is nanoseconds).
The default behaviour of this module is to skip leap seconds. This is what
(most versions of?) UNIX do. If you want to include leap seconds, set
skip_leap_seconds to false.
Some operating systems use an epoch defined in the local timezone of the
computer. If you want to use such an epoch in this module, you have two
options. The first is to submit a DateTime object with the appropriate
timezone. The second option is to set the local_epoch parameter to a true
value. In this case, you should submit an epoch with a floating timezone.
The exact epoch used in "format_datetime" will then depend on
the timezone of the object you pass to "format_datetime".
Most often, the time since an epoch is given in seconds. In some
circumstances however it is expressed as a number of days, hours, minutes
and seconds. This is done by NASA, for the so called Mission Elapsed Time.
For example, 2/03:45:18 MET means it has been 2 days, 3 hours, 45 minutes,
and 18 seconds since liftoff. If you set the dhms parameter to true,
format_datetime returns a four element list, containing the number of
days, hours, minutes and seconds, and parse_datetime accepts the same four
element list.
- •
- format_datetime($datetime)
Given a DateTime object, this method returns the number of seconds since the
epoch.
- •
- parse_datetime($secs)
Given a number of seconds, this method returns the corresponding DateTime
object.
BUGS¶
I think there's a problem when you define a count that does not skip leap
seconds, and uses the local timezone. Don't do that.
SUPPORT¶
Support for this module is provided via the datetime@perl.org email list. See
http://lists.perl.org/ for more details.
AUTHOR¶
Eugene van der Pijll <pijll@gmx.net>
COPYRIGHT¶
Copyright (c) 2003-2006 Eugene van der Pijll. All rights reserved. This program
is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.
SEE ALSO¶
DateTime
datetime@perl.org mailing list