java Date to c# ticks
in [Java Programming]
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From: Martin Gregorie on 5 Mar 2010 19:26 On Sat, 06 Mar 2010 10:02:22 +1300, Peter K wrote: > "Eric Sosman" <esosman(a)ieee-dot-org.invalid> wrote in message > news:hmr3jt$biv$1(a)news.eternal-september.org... >> On 3/4/2010 10:56 PM, Arne Vajhøj wrote: >>> On 03-03-2010 21:21, Eric Sosman wrote: >>>> On 3/3/2010 8:57 PM, Arne Vajhøj wrote: >>>>> On 03-03-2010 20:45, Eric Sosman wrote: >>>>>> On 3/2/2010 4:28 PM, Peter K wrote: >>>>>>> [...] >>>>>>> C# (.net) ticks are based on nanoseconds since 1/1/0001. >>>>>> >>>>>> Assertion: The low-order thirty-two bits of such a value at any >>>>>> given moment (NOW!) are unknown -- and unknowable. >>>>> >>>>> It is not 1 ns unit but 100 ns units. And the low 32 bits is around >>>>> 430 seconds. >>>> >>>> Thanks for the information. I'll revise my claim: "The low-order >>>> twenty-five bits are unknown and unknowable." >>>> >>>>> We do probably not have any measurements at 430 seconds accuracy for >>>>> year 1. But do have it today. And it would be rather inconvenient to >>>>> use different units for different periods. >>>> >>>> Intervals between contemporary events can (sometimes) be measured to >>>> nanosecond precision. In the laboratory, femtosecond precision may be >>>> attainable. But extending the scale to longer periods is pure >>>> fiction! Claim: You cannot measure the time between an event at >>>> lunchtime yesterday and one at lunchtime today with nanosecond >>>> precision. You probably can't measure it with millisecond precision, >>>> and even one-second precision would require a good deal of care. >>>> >>>> Even in one single lunch hour, you cannot measure the time between >>>> the swallow and the belch with nanosecond precision. >>> >>> All true. >>> >>> But still it is a lot easier to use the same unit for both long and >>> short intervals. >> >> I've no quarrel with measuring *intervals* in tiny units. >> The thing that started me ranting and foaming at the mouth was the >> statement that "C# (.net) ticks are based on nanoseconds since >> 1/1/0001." *That's* the association I regard as fiction, bordering on >> nonsense. > > Yes, sorry, I mis-wrote the definition from Microsoft. > > The .net DateTime structure represents dates and times ranging from > 1/1/0001 to 31/12/9999. The values are measured in 100ns units called > ticks. > > http://msdn.microsoft.com/en-us/library/system.datetime.aspx > > But is your quarrel that if I actually went back the billions of > nanoseconds from the value for today's nanasecond value, I wouldn't > actually end up at 1/1/0001 - due to vagaries in the Earth's orbit, spin > etc? > To say nothing of the transitions between the various calendars, which, over the mere 2009 years in that range are probably more significant than spin rate and orbit deviations. -- martin@ | Martin Gregorie gregorie. | Essex, UK org |
From: John Stockton on 6 Mar 2010 08:42 In comp.lang.java.programmer message <v0fuo5911s1bvrsmq1nq0g23kqke4t3pge(a)4ax.com>, Wed, 3 Mar 2010 20:52:42, Roedy Green <see_website(a)mindprod.com.invalid> posted >On Wed, 3 Mar 2010 22:56:52 +0000, Dr J R Stockton ><reply1009(a)merlyn.demon.co.uk> wrote, quoted or indirectly quoted >someone who said : >> >>Ten dates (no days) dropped. Later, parts of Canada dropped 11 dates. > >The full story is quite complex. Different parts of world accepted >the Gregorian calendar at different times. Indeed. But, knowing you to be in Canada, I gave it special treatment. It is said that mainland Nova Scotia changed from Gregorian to Julian (sic) previous to 1752. Can you give the last Gregorian and first Julian date at that change (one expects it to have occurred at local midnight), from trustworthy Canadian sources? > There are parts of the >world today still on the Julian calendar. I rather doubt whether any parts of the world still use it in their daily secular life. Russian (and other) Orthodox celebrate Easter by the Ju8lian Calendar and the pre-1752 (for us) rules. Mount Athos maybe uses the Greek Orthodox version, but they don't have a secular life. >BigDate works off two different definitions, the papal and the British >adoption. Those are different, but (when extrapolated as necessary in a reasonably obvious manner) give the same answers. I have seen part of the Canadian law on Easter, but not the most interesting part. Is it on line? -- (c) John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v6.07 IE 8. Web <URL:http://www.merlyn.demon.co.uk/> - w. FAQish topics, links, acronyms PAS EXE etc : <URL:http://www.merlyn.demon.co.uk/programs/> - see 00index.htm Dates - miscdate.htm moredate.htm js-dates.htm pas-time.htm critdate.htm etc.
From: Lew on 7 Mar 2010 23:37 Arne Vajhøj wrote: > Nanoseconds in year 1 is absurd. > > But it is not absurd to measure nanoseconds (or at least milliseconds > today). > > And it is not absurd to be able to store days many years back. > > And it is not absurd to use the same unit for all times. > > So we have now proven that: > 3 x not absurd = absurd Two wrongs don't make a right. But three lefts do. -- Lew
From: Lew on 7 Mar 2010 23:42 Peter K wrote: >> But is your quarrel that if I actually went back the billions of >> nanoseconds from the value for today's nanasecond value, I wouldn't >> actually end up at 1/1/0001 - due to vagaries in the Earth's orbit, spin >> etc? Martin Gregorie wrote: > To say nothing of the transitions between the various calendars, which, > over the mere 2009 years in that range are probably more significant than > spin rate and orbit deviations. I look at such a system (100 ns "ticks" since 0001-01-01T00:00:00.00...Z) as a "normalized" calendar/time system. Arguing that you cannot precisely measure 0001-01-01T00:00:00.00...Z as a number of ticks ago since NOW is specious; that datetime is *defined* by being that many ticks ago from NOW. So instead of trying to measure how many ticks ago "time zero" is, you now have the uncertainty of measuring how great was the wobble since then. Heisenberg. Tomayto/tomahto. Frequency/duration. Position/velocity. How many angels can dance on the head of a pin? (A: Depends on the caterer.) -- Lew
From: Dr J R Stockton on 8 Mar 2010 06:10
In comp.lang.java.programmer message <hmr3jt$biv$1(a)news.eternal- september.org>, Fri, 5 Mar 2010 09:14:18, Eric Sosman <esosman(a)ieee-dot- org.invalid> posted: > I've no quarrel with measuring *intervals* in tiny units. >The thing that started me ranting and foaming at the mouth was >the statement that "C# (.net) ticks are based on nanoseconds >since 1/1/0001." *That's* the association I regard as fiction, >bordering on nonsense. That's just due to the customary imprecision of US nerds. Those are GMT nanoseconds (no leap seconds); from Monday 0001-01-01 00:00:00 GMT = 0 ("since Jan 1" actually means "starting Jan 2"); and the days are of the proleptic Gregorian Calendar. IIRC, GMT there should actually be UT, but that will be taken as a typo for UTC. Januarius of that year actually started on the previous day. The Gregorian Calendar is valid perpetually from 1582-10-14, by Papal definition. If the civil calendar is ever changed, it will no longer be Gregorian. The proleptic extension is obvious, and has the authority of ISO 8601. A bad choice of start, too; arithmetic is simpler if the count starts at AD 0000 March 1, since that follows the rarest exceptional end-of- February. -- (c) John Stockton, nr London, UK. ?@merlyn.demon.co.uk Turnpike v6.05. Web <URL:http://www.merlyn.demon.co.uk/> - w. FAQish topics, links, acronyms PAS EXE etc : <URL:http://www.merlyn.demon.co.uk/programs/> - see 00index.htm Dates - miscdate.htm estrdate.htm js-dates.htm pas-time.htm critdate.htm etc. |