README

a civil date and time library for PHP

Motivation

A civil date, or civil time, is a date/time without any timezone specified.

Such an entity should not be used for representing a precise, absolute moment or period in time. However, it is a good way to represent the concept of a "calendar date" or "clock time" as it is used in many everyday contexts.

For example, if someone was born on 1 January 2000, then they will typically want to celebrate their birthday on 1 January each year, in whichever timezone they happen to be living in at the time. In other words, the entity "1 January 2000", insofar as it represents their date of birth, is timezone-agnostic.

In a software context, this might be important if, for example, we want to send an email to each user on their birthday, where each user may have a different timezone associated with them. A given user's timezone might change over time; but their date of birth will not. It is with the user that the timezone should be associated here—not with their date of birth.

While it's possible to use the standard library's DateTime or DateTimeImmutable to represent civil dates and times in PHP, it isn't ideal, as it requires an out-of-band convention about how to interpret the timezone information attached to such an object. (Should the timezone data merely be ignored? Should the date time be converted to UTC and then have its timezone ignored? Or should non-UTC DateTimes be considered invalid as representations of civil dates?)

A dedicated class, that omits timezone information by design, allows civil dates, times, and date-time pairings, to be represented cleanly and directly.

For additional concrete use cases for civil dates, times, and date-times, see this comment in relation to a similar library proposed for Go.

Installation

composer require matt-harvey/civil-date-time

Note this library is still in a pre-v1 state, and there may be breaking changes in any release. (Although, I will generally avoid making breaking changes in patch version releases.)

Usage

There are three classes offered:

• CivilDate
• CivilTime
• CivilDateTime

Each of these is immutable: methods such as CivilDate::addDays() always return new instances, rather than mutating the existing one.

Civil dates

use MattHarvey\CivilDateTime\CivilDate;

// 15 March 2022
new CivilDate(2022, 3, 15);

// or...
CivilDate::fromIsoDateStamp('2022-03-15');

// format - signature mirrors \DateTime::format
CivilDate::fromIsoDateStamp('2022-03-15')->format('D j M Y'); // 'Sat 15 Mar 2022'

// convenience method for ISO format
CivilDate::fromIsoDateStamp('2022-03-15')->toIsoDateStamp(); // 2022-03-15
// or just
CivilDate::fromIsoDateStamp('2022-03-15')->__toString(); // 2022-03-15

// converting from standard library \DateTimeInterface to CivilDate
// e.g., the moment that is 1:30pm in UTC on 22 Jan. 2021, falls on 23 January 2021 in Sydney
$dateTime = new DateTimeImmutable('2021-01-22 13:30:01+0');
$sydney = new DateTimeZone('Australia/Sydney');
CivilDate::forMomentInTimezone($dateTime, $sydney); // 23 January 2021

// immutable addition/subtraction of days
CivilDate::fromIsoDateStamp('2022-03-15')->addDays(3); // 18 March 2022
CivilDate::fromIsoDateStamp('2022-03-15')->addDays(-3); // 12 March 2022

// difference in days
$dayA = CivilDate::fromIsoDateStamp('2010-03-05');
$dayB = CivilDate::fromIsoDateStamp('2010-04-05');
CivilDate::diffDays($dayB, $dayA); // 31
CivilDate::diffDays($dayA, $dayB); // -31

// comparison
$dayB->laterThan($dayA); // true

// extracting components
$dayA->getYear(); // 2010
$dayA->getMonth(); // 3
$dayA->getDay(); // 5

Civil times

use MattHarvey\CivilDateTime\CivilTime;

$civilTime = new CivilTime(22, 11, 18);                // 10:11:18 p.m.
CivilTime::from24HoursStamp('22:11:18');               // 10:11:18 p.m.
CivilTime::from12HourClock(10, 11, 18, CivilTime::PM); // 10:11:18 p.m.

$civilTime->get24Hour();                               // 22
$civilTime->get12Hour();                               // 10
$civilTime->getMinute();                               // 11
$civilTime->getSecond();                               // 18
$civilTime->getAmPm();                                 // 'pm'

$civilTime->to24HourStamp();                           // '22:11:18'

$civilTimeB = new CivilTime(22, 11, 19);
$civilTimeB->laterThan($civilTime);                    // true

Civil date/times

use MattHarvey\CivilDateTime\CivilTime;
use MattHarvey\CivilDateTime\CivilDate;
use MattHarvey\CivilDateTime\CivilDateTime;

$civilDate = new CivilDate(2022, 3, 15);
$civilTime = new CivilTime(22, 11, 18);
$civilDateTime = new CivilDateTime($civilDate, $civilTime); // 10:11:18 p.m. on 15 Mar. 2022
CivilDateTime::fromIsoDateTimeStamp('2022-03-15T22:11:18');

$sydney = new DateTimeZone('Australia/Sydney');
$civilDateTime = new DateTimeImmutable('2021-06-26 20:34:05+10');
CivilDateTime::forMomentInTimezone($dateTime, $sydney); // 26 Jun. 2021, 8:34:05pm

// convert back
$civilDateTime->toDateTimeImmutable('Australia/Sydney'); // 26 Jun. 2021, 8:34:05pm, Australia/Sydney
// or
$civilDateTime->toDateTimeImmutable('Australia/Perth');  // 26 Jun. 2021, 8:34:05pm, Australia/Perth

Civil date/time in other PHP libraries

• https://github.com/brick/date-time offers the LocalDate, LocalTime and LocalDateTime classes, that are analogous to civil-date-time's CivilDate, CivilTime and CivilDateTime. It also offers classes for modelling many other date/time concepts, which civil-date-time doesn't do—including ZonedDateTime as a replacement for the standard library DateTimeImmutable. You might prefer it to civil-date-time if you're looking for a more extensive set of date/time utilities, rather than a minimal adjunct to the standard library to plug just the civil date/time gap.
• https://github.com/cakephp/chronos offers a Date class, which is notionally similar to civil-date-time's CivilDate; however it extends DateTimeImmutable and so carries a lot of redundant data as well as no-op functions inherited from the latter.

Civil date/time libraries in other programming languages

• Go: https://pkg.go.dev/cloud.google.com/go/civil
• C++: https://github.com/google/cctz

Contributing

PRs, bug reports, and suggestions are all welcome. Please ensure unit test coverage is maintained.

You will need xdebug installed to generate the coverage report.

composer test runs the test suite.