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A Tale about Time - PHP Limburg

A Tale about Time - PHP Limburg

Timezones, DST, human readable diffs, standardised formats, intervals, getting the last Tuesday of next month… Dealing with timestamps seems easy, but there’s a lot to it. It’s very easy to do it wrong. Learn how to do this properly and you’ll never be chasing weird time related bugs anymore!

Hannes Van De Vreken

December 05, 2019
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  1. A Tale about Time
    @hannesvdvreken
    @phplimburg

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  2. Hi, my name is Hannes.

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  3. Genk

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  4. Gent

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  6. A Tale about Time

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  7. The earth is a globe

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  8. Religion

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  9. Dec 5, 2019 8:30pm CET
    20:30, 5 december 2019
    2019-12-05T20:30:00+02:00

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  13. 360°
    60’
    60”

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  17. EDT = UTC-04:00
    CEST = UTC+02:00

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  21. EDT = UTC-04:00
    CEST = UTC+02:00

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  22. #
    UTC+05:30

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  23. UTC+05:45

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  24. DST
    CET/CEST

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  25. Helsinki
    Sunrise: 9:24 - 3:54
    Sunset: 15:13 - 22:50
    Quito
    Sunrise: 6:08 - 6:12
    Sunset: 18:16 - 18:19

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  28. 2019
    EDT/EST- March 10
    CET/CEST - March 31

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  29. $

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  31. %

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  33. &

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  34. '

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  35. Calendars

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  36. Weeks - 7 days
    Starts on Monday. Or Sunday?
    First week of the year?

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  37. Months
    Lunar vs Tropical

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  38. Years
    Lunisolar vs Tropical

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  39. 2018AD
    1500BC

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  40. Leap years

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  41. Leap years
    Leap seconds

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  42. Storing vs Expressing time

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  43. Expressing time:
    6:00PM vs 18:00 (ISO)

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  44. Expressing time:
    September 18
    09/18/2018
    18/09/2018
    2019-12-05

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  45. Storing time:
    1521261900 ($dt->timestamp)

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  46. Storing time:
    1521261900
    >1970-01-01T00:00:00+00:00
    <2038-01-19T03:14:07+00:00 (32bit)

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  47. Storing time:
    RFC3339:
    2018-03-17T10:15:00+05:30

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  48. Storing time:
    RFC3339 extended:
    2018-03-17T10:15:00.000+05:30

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  49. Storing time:
    Sortable (in UTC):
    2018-03-17T05:45:00.000+00:00

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  50. Storing time:
    Sortable (in UTC):
    2018-03-17T05:45:00.000+00:00
    + user’s location for timezone & locale

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  51. Storing time:
    Sortable (in UTC):
    2018-03-17T05:45:00.000+00:00
    + user’s location for timezone & locale
    (europe/brussels)

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  52. Time in PHP

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  53. date()
    microtime()

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  54. DateTimeInterface
    - DateTime (date, time, tz)
    - DateTimeImmutable

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  55. $date = DateTimeImmutable::createFromMutable($mutable);

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  56. Change in PHP 7.1: microseconds

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  57. // <7.1
    $date = new DateTimeImmutable(‘now’);
    $date->format(‘u’); // 00000
    // 7.1+
    $date = new DateTimeImmutable(‘now’);
    $date->format(‘u’); // actual microsecond info

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  58. // Immutable
    $whenInRome = $date->setTimezone('Europe/Rome');

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  59. // Magic
    $date = new DateTimeImmutable('now');
    $date = $date->modify('first day of next month');

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  60. “now + 5 hours”
    “first day of next month”
    "first weekday”

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  61. “2016-03-00” → “2016-02-29”
    “2018-06-31” → “2018-07-01”

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  62. “69-12-31” → “2069-12-31”
    “70-01-01” → “1970-01-01”

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  63. nesbot/carbon - Mutable
    cakephp/chronos - Immutable
    $now->diffForHumas($date);

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  64. interface Clock
    {
    public function now(): DateTimeImmutable
    }
    class SystemClock implements Clock
    class TestClock implements Clock

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  65. The future

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  66. E=mc²

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  67. c ~ 299.000.000m/s

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  71. Warping up

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  72. Wrapping up

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  73. Thanks for your time!
    @hannesvdvreken
    @phplimburg

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  74. Time for questions.
    @hannesvdvreken
    @phplimburg

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