Time Zones Will Ruin Your Day

Questions

1. 1
   Not answered. What does getDate() return here on a server running in America/New_York?
2. 2
   Not answered. Why do new Date("2026-01-15") and new Date("2026-01-15T00:00:00") produce different instants?
3. 3
   Not answered. What integer does new Date("2026-01-15T12:00:00Z").getTimezoneOffset() return with TZ=America/New_York?
4. 4
   Not answered. What time zone does a JavaScript Date instance store internally?
5. 5
   Not answered. A client sends 2026-07-04T12:00:00-04:00. What can you conclude about the sender's time zone?
6. 6
   Not answered. What UTC offset does the IANA zone Etc/GMT+5 actually have?
7. 7
   Not answered. How does the time zone identifier EST behave differently from America/New_York?
8. 8
   Not answered. How many instants correspond to 2026-03-08T02:30:00 in America/New_York?
9. 9
   Not answered. With Temporal's default disambiguation, what instant does 2026-03-08T02:30 in New York resolve to?
10. 10
    Not answered. Which Temporal disambiguation value makes an impossible or ambiguous local time throw instead of resolve?
11. 11
    Not answered. Why can two log lines timestamped 2026-11-01 01:15 and 2026-11-01 01:45 in New York be 90 minutes apart?
12. 12
    Not answered. Why does 2026-11-01T01:30:00-04:00[America/New_York] carry both an offset and a zone name?
13. 13
    Not answered. What wall-clock time results from adding 86,400,000 ms to midnight on 2026-03-08 in New York?
14. 14
    Not answered. How many hours pass between a 09:00 New York meeting on 2026-03-07 and the next one on 2026-03-08?
15. 15
    Not answered. Which values should be stored as wall time plus an IANA zone rather than as a UTC instant?
16. 16
    Not answered. A 2023 meeting stored as a UTC instant fired an hour late for Mexican attendees. Why?
17. 17
    Not answered. Why is a date of birth the wrong thing to store in a timestamp column?
18. 18
    Not answered. Which Temporal type models "May 14" as a recurring anniversary with no year attached?
19. 19
    Not answered. Why does Temporal provide startOfDay() instead of letting you set the time to 00:00?
20. 20
    Not answered. What does hoursInDay return for a New York ZonedDateTime on 2026-03-08?
21. 21
    Not answered. By how many minutes does Lord Howe Island shift its clocks for daylight saving?
22. 22
    Not answered. How many minutes ahead of UTC is Asia/Kathmandu?
23. 23
    Not answered. How many different calendar dates can be in use around the world at the same moment?
24. 24
    Not answered. How many hours ahead of UTC is the furthest-forward time zone in regular use?
25. 25
    Not answered. Which ISO 8601 week date does the calendar date 2025-12-29 have?
26. 26
    Not answered. What is the difference between the ISO 8601 durations P1M and PT1M?
27. 27
    Not answered. Which timestamps are valid ISO 8601 but rejected by RFC 3339?
28. 28
    Not answered. In RFC 3339, how does the offset -00:00 differ from +00:00?
29. 29
    Not answered. When is sorting ISO 8601 timestamp strings lexicographically the same as sorting by instant?
30. 30
    Not answered. How does POSIX "seconds since the Epoch" handle a leap second?
31. 31
    Not answered. By how many seconds does TAI lead UTC as of 2026?
32. 32
    Not answered. What did the 2022 General Conference on Weights and Measures decide about leap seconds?
33. 33
    Not answered. Why should elapsed-time measurements not use the wall clock?
34. 34
    Not answered. How many distinct UTC offsets does the abbreviation CST refer to in common use?
35. 35
    Not answered. What does PostgreSQL physically store in a timestamptz column?
36. 36
    Not answered. What type and value does timestamptz '2026-01-15 12:00:00+00' AT TIME ZONE 'America/New_York' produce?
37. 37
    Not answered. Why is BETWEEN '2026-01-15 00:00' AND '2026-01-15 23:59:59.999' the wrong way to select one day?
38. 38
    Not answered. How does MySQL's TIMESTAMP type differ from DATETIME in its handling of zones?
39. 39
    Not answered. An API sends "createdAt": 1767225600 and the UI renders January 1970. What went wrong?
40. 40
    Not answered. What is the largest value a signed 32-bit time_t can hold?
41. 41
    Not answered. What does JSON.stringify({ at: new Date(NaN) }) produce?
42. 42
    Not answered. Does 2026-01-30 plus one month plus one day equal the same date as plus one day plus one month?
43. 43
    Not answered. Why does the tz database model Europe/Dublin as having negative daylight saving in winter?
44. 44
    Not answered. What happened to Friday, 30 December 2011 in Samoa?
45. 45
    Not answered. What offset does the tz database record for Brussels before standard time was adopted?
46. 46
    Not answered. Why do Morocco's clock changes fall on different dates each year?
47. 47
    Not answered. How does iCalendar keep a weekly meeting on the same wall clock across a DST change?
48. 48
    Not answered. How many hours does a New York night shift from 22:00 on 2026-10-31 to 06:00 on 2026-11-01 last?
49. 49
    Not answered. How should a browser determine the user's IANA time zone?
50. 50
    Not answered. Why did calendar software show wrong times in March 2007 in the United States?