<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto">Firstly, I wrote a RealTimeClock background task for ProjectOberon that increments Kernel.clock based on Kernel.timer. My SW accuracy is almost as high as a HW RTC.<div><br></div><div>Secondly, here are two approaches to fix this 63 years restriction of the current implementation</div><div>a) 100 years are less than 2^32 seconds, so we can fit them in 32 bits but we cant use powers of 2 anymore to split the fields.</div><div>b) use a granularity of 2 seconds for clock iso 1 second. Then you get 1 bit more for the year and you can code the year from 00..99</div><div><br></div><div>I did not make up my mind whether a) or b) is better, or we should just live with the restriction and set the base year to eg 2010. Then the problem only appears in 2073.<br><div><br><div><div dir="ltr"><div>Jörg</div></div><div dir="ltr"><br><blockquote type="cite">Am 13.02.2020 um 20:36 schrieb Charles Perkins <chuck@kuracali.com>:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr"><div dir="ltr"><div>I'm writing a linux kernel filesystem driver for Project Oberon disk images and I'm wondering how best to interpret the Date field in the FileDesc record. </div><div><br></div><div>It looks to me like the Files module just puts the latest Kernel.Clock() value in there when the file is written.</div><div><br></div><div>System.Mod sets the date value like this:</div><div><span style="color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">dt </span><span class="gmail-pl-smi" style="box-sizing:border-box;color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">:=</span><span style="color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre"> </span><span class="gmail-pl-smi" style="box-sizing:border-box;color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">((((</span><span style="color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">yr</span><span class="gmail-pl-smi" style="box-sizing:border-box;color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">*</span><span class="gmail-pl-c1" style="box-sizing:border-box;color:rgb(0,92,197);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">16</span><span style="color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre"> </span><span class="gmail-pl-smi" style="box-sizing:border-box;color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">+</span><span style="color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre"> mo</span><span class="gmail-pl-smi" style="box-sizing:border-box;color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">)*</span><span class="gmail-pl-c1" style="box-sizing:border-box;color:rgb(0,92,197);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">32</span><span style="color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre"> </span><span class="gmail-pl-smi" style="box-sizing:border-box;color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">+</span><span style="color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre"> day</span><span class="gmail-pl-smi" style="box-sizing:border-box;color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">)*</span><span class="gmail-pl-c1" style="box-sizing:border-box;color:rgb(0,92,197);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">32</span><span style="color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre"> </span><span class="gmail-pl-smi" style="box-sizing:border-box;color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">+</span><span style="color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre"> hr</span><span class="gmail-pl-smi" style="box-sizing:border-box;color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">)*</span><span class="gmail-pl-c1" style="box-sizing:border-box;color:rgb(0,92,197);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">64</span><span style="color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre"> </span><span class="gmail-pl-smi" style="box-sizing:border-box;color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">+</span><span style="color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre"> min</span><span class="gmail-pl-smi" style="box-sizing:border-box;color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">)*</span><span class="gmail-pl-c1" style="box-sizing:border-box;color:rgb(0,92,197);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">64</span><span style="color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre"> </span><span class="gmail-pl-smi" style="box-sizing:border-box;color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">+</span><span style="color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre"> sec</span><span class="gmail-pl-smi" style="box-sizing:border-box;color:rgb(36,41,46);font-family:SFMono-Regular,Consolas,"Liberation Mono",Menlo,monospace;font-size:12px;white-space:pre">;</span><br></div><div dir="ltr"><br></div><div>It looks to me like the above formula leaves 6 bits for the year, which means it ranges from 0 to 63.</div><div><br></div><div>Now I know that the FPGA doesn't actually have a real time clock and I think the time is always actually zero unless you set it to something else. I don't think it gets updated from the system millisecond timer either.</div><div><br></div><div>I'm just wondering if historically that year value that goes in a file header has a base year or other meaning. Without something like that the maximum year is "63" which is a long time ago!</div><div><br></div><div>I'd like to put something meaningful in this field when I move files in and out of Linux.</div><div><br></div><div>Anybody have a good idea? Should I just make it based on Jan 1 1970 like Unix, in which case it rolls over in 2033?</div><div><br></div><div>Am I over-thinking this? </div><div><br></div><div>Chuck</div><div dir="ltr"><br></div><br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><br>
</blockquote></div></div>
<span>--</span><br><span>Oberon@lists.inf.ethz.ch mailing list for ETH Oberon and related systems</span><br><span>https://lists.inf.ethz.ch/mailman/listinfo/oberon</span><br></div></blockquote></div></div></div></body></html>