Robin Pokorny 2025-05-28 Complexity of Clocks, Calendars, and Computers

2 Intro WHAT IS THE ?

Intro 3 The twenty-eighth of May, two thousand and twenty-five at two o’clock in the afternoon

History 4 HUMAN-MADE

5 History GOLDEN RATIO?

6 Example 28 May 2025, 2 pm

Example 2025-05-28T14:00:00 7

Example 2025-05-28T14:00:00 8

9 Example 20250528T140000

Example 2025-W22-3T14:00:00 10

11 Example 2025W223T140000

12 Example 2025-148T14:00:00 2025148T140000

Unix time: seconds or milliseconds? 1748433600000 1748433600 14

15 Solution for computers WHAT TO DO USE RFC 3339 DO NOT USE ISO

Example 16 2025-05-28T14:00:00+02:00 2025-05-28T12:00:00Z

Compare 17 Source

18 Solution for computers WHAT TO DO USE RFC 9557 Internet Extended Date/Time Format (IXDTF) USE RFC 3339 DO NOT USE ISO

Example 19 2025-05-28T14:00:00+02:00[Europe/Prague] 2025-05-28T12:00:00Z[Europe/Prague]

20 Example 2025-01-28T14:00:00+02:00[Europe/Prague] Inconsistent

21 Example 2035-05-28T13:00:00+01:00[Europe/Prague] Inconsistent

22 Temporal API Temporal API Upcoming replacement for the Date object with full RFC 9557 (IXDTF) support and time zone arithmetic.

Temporal API 23 Gist

24 Cheat sheet Storage and transport Y Instant? Y Past? N RFC 3339/9557 with Z Unix timestamp RFC 9557 (Local/Z + zone) N RFC 9557 (Local + zone) by robinpokorny.com

Solution for people Wednesday, 28 May 2025, 2 pm (Prague) Wed, 28 May, 2 pm PRG 25

Thanks THINK ABOUT YOUR DATES! me@robinpokorny.com 26