A Tale about Time - PHP.gent

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 @phpgent
2. Hi, my name is Hannes.
3. !
6. A Tale about Time
7. 2018-09-18T19:00:00+02:00
13. EDT = UTC-04:00 CEST = UTC+02:00
16. EDT = UTC-04:00 CEST = UTC+02:00
17. ' UTC+05:30
18. UTC+05:45
19. DST CET/CEST
20. Helsinki Sunrise: 9:24 - 3:54 Sunset: 15:13 - 22:50 Quito Sunrise: 6:08 - 6:12 Sunset: 18:16 - 18:19
23. EST/EDT - March 12 CET/CEST - March 24
24. (
25. )/*
26. Calendars
27. Weeks - 7 days Starts on Monday. Or Sunday? First week of the year?
28. Months Lunar vs Tropical
29. Years Lunisolar vs Tropical
30. 2018AD 1500BC
31. Leap years
32. Leap years Leap seconds
33. Storing vs Expressing time
34. Expressing time: 6:00PM vs 18:00
35. Expressing time: September 18 09/18/2018 18/09/2018
36. Storing time: 1521261900 ($dt->timestamp)
37. Storing time: 1521261900 >1970-01-01T00:00:00+00:00 <2038-01-19T03:14:07+00:00 (32bit)
38. Storing time: RFC3339: 2018-03-17T10:15:00+05:30
39. Storing time: RFC3339 extended: 2018-03-17T10:15:00.000+05:30
40. Storing time: Sortable (in UTC): 2018-03-17T05:45:00.000+00:00
41. Storing time: Sortable (in UTC): 2018-03-17T05:45:00.000+00:00 + user’s location for timezone & locale
42. Storing time: Sortable (in UTC): 2018-03-17T05:45:00.000+00:00 + user’s location for timezone & locale (europe/brussels)
43. Time in PHP
44. date() microtime()
45. DateTimeInterface - DateTime (date, time, tz) - DateTimeImmutable
46. $date = DateTimeImmutable::createFromMutable($mutable);
47. Change in PHP 7.1: microseconds
48. // <7.1 $date = new DateTimeImmutable(‘now’); $date->format(‘u’); // 00000 // 7.1+ $date = new DateTimeImmutable(‘now’); $date->format(‘u’); // actual microsecond info
49. $date = $date->setTimezone('Europe/Rome');
50. // Magic $date = new DateTimeImmutable('now'); $date = $date->modify('first day of next month');
51. “now + 5 hours” “first day of next month” "first weekday” …
52. “2016-03-00” → “2016-02-29” “2018-06-31” → “2018-07-01” …
53. “69-12-31” → “2069-12-31” “70-01-01” → “1970-01-01” …
54. nesbot/carbon - Mutable cakephp/chronos - Immutable
55. interface Clock { public function now(): DateTimeImmutable } class SystemClock implements Clock class TestClock implements Clock
56. The future
57. E=mc²
58. c ~ 299.000.000m/s
62. Wrapping up
63. Thanks for your time! @hannesvdvreken @phpgent
64. Time for questions. @hannesvdvreken @phpgent