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Geeks celebrate RISC OS time epoch

Published: 20th Nov 2008, 12:12:51 | Permalink | Printable

Clock-watching nerds rejoiced this week as all modern ROS machines reached a mildly baffling milestone. The OS keeps track of the current time by storing it as the number of one hundredths of a second elapsed since midnight January 1, 1900 - and this figure ticked over to 0x5000000000 in the early hours of Tuesday, provoking excitement among some.

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Stuart really, really needs to get out more!

 is a RISC OS Userdruck on 20/11/08 1:22PM
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Except it was JGH who started it.

 is a RISC OS UserIvanDobski on 21/11/08 10:43AM
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Ah, I'd been seeing some of this epoch news, but hadn't been able to access my RISC OS machine to investigate. Is this all it is? From the name I assumed it was an issue like the year 2038 bug, but actually it's just the 39th bit being set for the first time, which is fine unless you're using a signed 39-bit number for storing date/time info (or an unsigned 38-bit one).

How does filecore store the date, by the way? When will RISC OS actually risk running out of dates?

 is a RISC OS Userninja on 21/11/08 2:40PM
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ninja: FileCore stores them in the full 40bit format.

 is a RISC OS Userrjek on 21/11/08 3:36PM
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There is no bug, and RISC OS centiseconds since 1900 datestamps are good to go up to the year 2248, 141 years after UNIX seconds since 1970 datestamp run out in 2106.

As its a multi word 40bit number I don't see any problems when it goes negative in 2174, unlike systems using 32bit UNIX datestamps in 2038 which are likely to have issues due to signed arthimetic.

 is a RISC OS Userdruck on 21/11/08 11:32PM
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rjek@trite:~$ cat test.c #include <stdio.h> #include <time.h>

main() { printf("%d\n", sizeof(time_t)); }

rjek@trite:~$ ./a.out 8

 is a RISC OS Userrjek on 21/11/08 11:56PM
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Buh, drobe's reformatted my comment insanely. Anyway, on almost all modern UNIX systems, time_t is 64 bit.

 is a RISC OS Userrjek on 21/11/08 11:56PM
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If we were discussing modern systems, we wouldn't be talking about...

 is a RISC OS Userdruck on 24/11/08 9:02AM
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