A Tale about Time - PHPDay 2018

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 @phpday
2. Hi, my name is Hannes.
3. This is a 50 minute talk in 25 minutes.
4. “We'd like to start the happy hour 30 minutes earlier than previously planned … and the best solution would be to move your talk”
9. EDT = UTC-04:00 CEST = UTC+02:00
12. EDT = UTC-04:00 CEST = UTC+02:00
13. # UTC+05:30
14. UTC+05:45 $
15. DST CET/CEST
16. Helsinki Sunrise: 9:24 - 3:54 Sunset: 15:13 - 22:50 Quito Sunrise: 6:08 - 6:12 Sunset: 18:16 - 18:19
19. EST/EDT - March 12 CET/CEST - March 24
20. %
21. &/'
22. Calendars
23. Weeks - 7 days Starts on Monday. Or Sunday? First week of the year?
24. Months Lunar vs Tropical
25. Years Lunisolar vs Tropical
26. 2018AD 1500BC
27. Leap years
28. Leap years Leap seconds
29. Storing vs Expressing time
30. Expressing time: 6:00PM vs 18:00
31. Expressing time: May 12 12/05/2018
32. Storing time: 1521261900
33. Storing time: 1521261900 >1970-01-01T00:00:00+00:00
34. Storing time: 1521261900 >1970-01-01T00:00:00+00:00 <2038-01-19T03:14:07+00:00 (32bit)
35. Storing time: RFC3339: 2018-03-17T10:15:00+05:30
36. Storing time: RFC3339 extended: 2018-03-17T10:15:00.000+05:30
37. Storing time: Sortable (in UTC): 2018-03-17T05:45:00.000+00:00
38. Storing time: Sortable (in UTC): 2018-03-17T05:45:00.000+00:00 + user’s location for timezone & locale
39. Time in PHP
40. DateTimeInterface - DateTime (date, time, tz) - DateTimeImmutable
41. $date = DateTimeImmutable::createFromMutable($mutable);
42. Change in PHP 7.1: microseconds
43. $date = $date->setTimezone('Europe/Rome');
44. // Magic $date = new DateTimeImmutable('now'); $date = $date->modify('first day of next month');
45. “now + 5 hours” “first day of next month” "first weekday” …
46. “2016-03-00” → “2016-02-29” “2018-06-31” → “2018-07-01” …
47. “69-12-31” → “2069-12-31” “70-01-01” → “1970-01-01” …
48. nesbot/carbon - Mutable cakephp/chronos - Immutable
49. interface Clock { public function now(): DateTimeImmutable }
50. The future
51. E=mc²
52. c ~ 299.000.000m/s
56. (new DateTimeImmutable(‘now’)) ->setPlanet(new Planet(‘mars’));
57. Wrapping up
58. Thanks for your time! @hannesvdvreken @phpday
59. Time for questions. @hannesvdvreken @phpday