1. 1
2. 2
3. 3
4. 4
5. 5
6. 6
7. 7
8. 8
9. 9
10. 10
11. 11
12. 12
13. 13
14. 14
15. 15
16. 16
17. 17
18. 18
19. 19
20. 20
21. 21
22. 22
23. 23
24. 24
25. 25
26. 26
27. 27
28. 28
29. 29
30. 30
31. 31
32. 32
33. 33
34. 34
35. 35
36. 36
37. 37
38. 38
39. 39
40. 40
41. 41
42. 42
43. 43
44. 44
45. 45
46. 46
47. 47
48. 48
49. 49
50. 50
51. 51
52. 52
53. 53
54. 54
55. 55
56. 56
57. 57
58. 58
59. 59
60. 60
61. 61
62. 62
63. 63
64. 64
65. 65
66. 66
67. 67
68. 68
69. 69

// Copyright 2025 Shota FUJI <pockawoooh@gmail.com>
// SPDX-License-Identifier: MIT
//
// ===
//
// This script scans every "<time>" elements with "data-local-format" attribute,
// replaces each element's text node with local datetime.
// If a "<time>" element does not have valid "datetime" attribute, this script
// skips the "<time>" element.
//
// "data-local-format" attribute accepts one of the below:
// - "datetime" ... displays date and time (default)
// - "date"     ... displays date
// - "time"     ... displays time
//
// This script intentionally uses scratch serialization instead of locale-aware
// APIs; locale strings often includes non-English characters thus does not
// incorporate with the rest of a page. As majority of readers are familiar with
// softwares, using RFC3339-ish style date and time format fits better than an
// uncontrollable locale string.

function toTimeString(date) {
	return date.getHours().toString().padStart(2, "0") + ":"
		+ date.getMinutes().toString().padStart(2, "0") + ":"
		+ date.getSeconds().toString().padStart(2, "0");
}

function toDateString(date) {
	// I don't expect this software/code will survive for 8000yrs.
	return date.getFullYear().toString().padStart(4, "0") + "-"
		// stupid spec made by American
		+ (date.getMonth() + 1).toString().padStart(2, "0") + "-"
		+ date.getDate().toString().padStart(2, "0");
}

function toDateTimeString(date) {
	return toDateString(date) + " " + toTimeString(date);
}

const targets = document.querySelectorAll("time[data-local-format]");
for (const target of targets) {
	const datetime = target.dateTime && Date.parse(target.dateTime);
	if (Number.isNaN(datetime)) {
		continue;
	}

	const originalText = target.textContent.trim();

	switch (target.dataset.localFormat || "datetime") {
		case "datetime":
			target.textContent = toDateTimeString(new Date(datetime));
			break;
		case "date":
			target.textContent = toDateString(new Date(datetime));
			break;
		case "time":
			target.textContent = toTimeString(new Date(datetime));
			break;
		default:
			console.warn(
				`Found unknown value on data-local-format attribute: "${target.dataset.localFormat}".\n`
					+ `Available values are: "datetime", "date", "time"\n`
					+ "Skipping text replacement.",
			);
			break;
	}

	target.title = originalText;
}