/src/wireshark/wsutil/epochs.h
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1 | | /** @file |
2 | | * |
3 | | * Definitions of epoch values for various absolute time types. |
4 | | * |
5 | | * Wireshark - Network traffic analyzer |
6 | | * By Gerald Combs <gerald@wireshark.org> |
7 | | * Copyright 2006 Gerald Combs |
8 | | * |
9 | | * SPDX-License-Identifier: GPL-2.0-or-later |
10 | | */ |
11 | | |
12 | | #ifndef __EPOCHS_H__ |
13 | | #define __EPOCHS_H__ |
14 | | |
15 | | #include <glib.h> |
16 | | |
17 | | /* |
18 | | * Deltas between the epochs for various non-UN*X time stamp formats and |
19 | | * the January 1, 1970, 00:00:00 (proleptic?) UTC epoch for the UN*X time |
20 | | * stamp format. |
21 | | */ |
22 | | |
23 | | /* |
24 | | * 1900-01-01 00:00:00 (proleptic?) UTC. |
25 | | * Used by a number of time formats. |
26 | | */ |
27 | 247 | #define EPOCH_DELTA_1900_01_01_00_00_00_UTC 2208988800U |
28 | | |
29 | | /* |
30 | | * 1904-01-01 00:00:00 (proleptic?) UTC. |
31 | | * Used in the classic Mac OS, and by formats, such as MPEG-4 Part 14 (MP4), |
32 | | * which is based on Apple's QuickTime format. |
33 | | */ |
34 | 0 | #define EPOCH_DELTA_1904_01_01_00_00_00_UTC 2082844800U |
35 | | |
36 | | /* |
37 | | * 1601-01-01 (proleptic Gregorian) 00:00:00 (proleptic?) UTC. |
38 | | * The Windows NT epoch, used in a number of places, as it is |
39 | | * the start of a 400 year Gregorian cycle. |
40 | | * |
41 | | * This is |
42 | | * |
43 | | * 369*365.25*24*60*60-(3*24*60*60+6*60*60) |
44 | | * |
45 | | * or equivalently, |
46 | | * |
47 | | * (89*4*365.25+(3*4+1)*365)*24*60*60 |
48 | | * |
49 | | * 1970-1601 is 369; 365.25 is the average length of a year in days, |
50 | | * including leap years. |
51 | | * |
52 | | * 369 = 4*92 + 1, so there are 92 groups of 4 consecutive years plus |
53 | | * one leftover year, 1969, with 365 days. |
54 | | * |
55 | | * All but three of the groups of 4 consecutive years average 365.25 days |
56 | | * per year, as they have one leap year in the group. However, 1700, 1800, |
57 | | * and 1900 were not leap years, as, while they're all evenly divisible by 4, |
58 | | * they're also evenly divisible by 100, but not evenly divisible by 400. |
59 | | * |
60 | | * So we have 89 groups of 4 consecutive years that average 365.25 |
61 | | * days per year, 3 groups of 4 consecutive years that average 365 days |
62 | | * (as they lack a leap year), and one leftover year, 1969, that is |
63 | | * 365 days long. |
64 | | */ |
65 | 625 | #define EPOCH_DELTA_1601_01_01_00_00_00_UTC UINT64_C(11644473600) |
66 | | |
67 | | /* |
68 | | * 2000-01-01 00:00:00 UTC. |
69 | | * Used by the Zigbee Zigbee Cluster Library protocol. |
70 | | */ |
71 | 503 | #define EPOCH_DELTA_2000_01_01_00_00_00_UTC ((unsigned)(((3*365 + 366)*7 + 2*365)*24*3600)) |
72 | | |
73 | | #endif /* __EPOCHS_H__ */ |