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!

Transcript

1. A Tale about Time @hannesvdvreken @phplimburg
2. Hi, my name is Hannes.
3. Genk
4. Gent
6. A Tale about Time
7. The earth is a globe
8. Religion
9. Dec 5, 2019 8:30pm CET 20:30, 5 december 2019 2019-12-05T20:30:00+02:00
13. 360° 60’ 60”
17. EDT = UTC-04:00 CEST = UTC+02:00
21. EDT = UTC-04:00 CEST = UTC+02:00
22. # UTC+05:30
23. UTC+05:45
24. DST CET/CEST
25. Helsinki Sunrise: 9:24 - 3:54 Sunset: 15:13 - 22:50 Quito Sunrise: 6:08 - 6:12 Sunset: 18:16 - 18:19
28. 2019 EDT/EST- March 10 CET/CEST - March 31
29. $
31. %
33. &
34. '
35. Calendars
36. Weeks - 7 days Starts on Monday. Or Sunday? First week of the year?
37. Months Lunar vs Tropical
38. Years Lunisolar vs Tropical
39. 2018AD 1500BC
40. Leap years
41. Leap years Leap seconds
42. Storing vs Expressing time
43. Expressing time: 6:00PM vs 18:00 (ISO)
44. Expressing time: September 18 09/18/2018 18/09/2018 2019-12-05
45. Storing time: 1521261900 ($dt->timestamp)
46. Storing time: 1521261900 >1970-01-01T00:00:00+00:00 <2038-01-19T03:14:07+00:00 (32bit)
47. Storing time: RFC3339: 2018-03-17T10:15:00+05:30
48. Storing time: RFC3339 extended: 2018-03-17T10:15:00.000+05:30
49. Storing time: Sortable (in UTC): 2018-03-17T05:45:00.000+00:00
50. Storing time: Sortable (in UTC): 2018-03-17T05:45:00.000+00:00 + user’s location for timezone & locale
51. Storing time: Sortable (in UTC): 2018-03-17T05:45:00.000+00:00 + user’s location for timezone & locale (europe/brussels)
52. Time in PHP
53. date() microtime()
54. DateTimeInterface - DateTime (date, time, tz) - DateTimeImmutable
55. $date = DateTimeImmutable::createFromMutable($mutable);
56. Change in PHP 7.1: microseconds
57. // <7.1 $date = new DateTimeImmutable(‘now’); $date->format(‘u’); // 00000 // 7.1+ $date = new DateTimeImmutable(‘now’); $date->format(‘u’); // actual microsecond info
58. // Immutable $whenInRome = $date->setTimezone('Europe/Rome');
59. // Magic $date = new DateTimeImmutable('now'); $date = $date->modify('first day of next month');
60. “now + 5 hours” “first day of next month” "first weekday” …
61. “2016-03-00” → “2016-02-29” “2018-06-31” → “2018-07-01” …
62. “69-12-31” → “2069-12-31” “70-01-01” → “1970-01-01” …
63. nesbot/carbon - Mutable cakephp/chronos - Immutable $now->diffForHumas($date);
64. interface Clock { public function now(): DateTimeImmutable } class SystemClock implements Clock class TestClock implements Clock
65. The future
66. E=mc²
67. c ~ 299.000.000m/s
71. Warping up
72. Wrapping up
73. Thanks for your time! @hannesvdvreken @phplimburg
74. Time for questions. @hannesvdvreken @phplimburg