Re: [Lazarus] Debugging Wince shows NO debugger output
Am 13.11.2013 22:49, schrieb Martin: On 13/11/2013 20:40, GREP wrote: Hi I could not get the breakpoints to work, I googled a lot, tried all the suggestions unsuccessfully. After a full day of trial I ended up that now the project does not show anything in the Debugger output window. I have this setup Windows XP, lazarus 1.0,12, svn 42478 Not sure, never done wince. But you can try and sent a log http://wiki.lazarus.freepascal.org/GDB_Debugger_Tips#Log_info_for_debug_session Maybe something stands out. I mention this as something that stands out for quite some time already: http://bugs.freepascal.org/view.php?id=21061 Regards, Sven -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] Debugging Wince shows NO debugger output
Am 13.11.2013 21:40, schrieb GREP: Hi I could not get the breakpoints to work, I googled a lot, tried all the suggestions unsuccessfully. Did you find this bug report http://bugs.freepascal.org/view.php?id=21061 on your search? (and also the related ones) Regards, Sven -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] Lazarus 1.2RC1 Ctrl-F9 not working
On Wed, Nov 13, 2013 at 11:17:59PM +0100, Bart wrote: On 11/13/13, Mattias Gaertner nc-gaert...@netcologne.de wrote: Check your short cuts in your system settings. They take precedence over any normal application like the IDE. On my Fedora 18 / KDE Ctrl+F9 does something weird to the windows that I cannot really describe or give a name. I'm too lazy to look it up and disable it. (On my old Suse 10.0 disabling system setting for Ctrl+F9 took me 2 days to find...) In case anyone is struggling to find it in XFCE: Settings-Window Manager-Keyboard. Disable the shortcut for Workspace 9. Henry -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
On Thu, 14 Nov 2013 07:19:56 +0100 Jürgen Hestermann juergen.hesterm...@gmx.de wrote: Am 2013-11-13 19:42, schrieb Reimar Grabowski: 1 julian year = 365.25 days of 86400 SI seconds each. Of course there are lots of other definitions for year but if FPC uses the julian one the value is exact and no approximation So the difference between 2007-01-01 12:00 and 2008-01-01 12:00 ist *not* one year? It is not one julian year. There is nothing like a year. As i said there are different definitions. If you talk about calendar year it's length changes and is therefor not a good measure of time and not used in science. It's only 365,00 days and therefore not a full year according to your definition. Correct. And this is not my definition it is the correct definition of a julian year and it is based on SI units. Time is measured in SI seconds. If you cannot express 'your year' as seconds it is not a unit of time. But this it totaly wrong. Care to elaborate? Or is it just your gut feeling? Same day same time of one year and the next should always be a one year difference. According to what definition of year? Calendar year is a rather poor unit to measure time differences as it is not constant and cannot be expressed in seconds. R. -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
On Thu, 14 Nov 2013 07:56:16 +0100 Patrick Chevalley p...@ap-i.net wrote: All this efforts are to bypass the problem with the calendar year (the one you mention) because it is sometime 365 and sometime 366 days. This is a totally unacceptable definition when you need an homogeneous time scale. So all depend of the use you need for your application and it must be admitted that one set of definition/function is not sufficient and every one must be careful when using time period. +1 R. -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
On Wed, 13 Nov 2013 20:34:36 +0100 John Landmesser joh...@online.de wrote: What about Databases like mysql, Oracle, Firebird. I'm shure they have such a function. For MySQL: DATEDIFF(expr1,expr2) DATEDIFF() returns expr1 – expr2 expressed as a value in days from one date to the other. expr1 and expr2 are date or date-and-time expressions. Only the date parts of the values are used in the calculation. :) R. -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
El 14/11/2013 7:56, Patrick Chevalley escribió: All this efforts are to bypass the problem with the calendar year (the one you mention) because it is sometime 365 and sometime 366 days. This is a totally unacceptable definition when you need an homogeneous time scale. Hello, I was following this thread about the years, months, days, datediff and almost all people expect that dates: 2013/05/15 - 2013/07/16 Return 2 months + 1 day, but I expect it to return 1 month and 16+16 days, because month definition out of context is around 30.43 So in the above example for sure 1 months has been passed and 32 days, then you can decide if 32 days is 1 month plus or not. The same applies to years: 1999/02/28 - 2000/02/29 = 1 Year 2000/02/27 - 2001/02/28 = 1 Year + 1 day 2000/02/28 - 2001/02/28 = 1 Year 2000/02/29 - 2001/02/28 = 1 Year 2000/02/29 - 2001/03/01 = 1 Year + 1 day 2001/05/2 - 2002/06/30 = 1 Year + 29+30 days Maybe I'm completly wrong ? -- -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
On 14.11.2013 10:50, Reimar Grabowski wrote: For MySQL: DATEDIFF(expr1,expr2) DATEDIFF() returns expr1 – expr2 expressed as a value in days from one date to the other. expr1 and expr2 are date or date-and-time expressions. Only the date parts of the values are used in the calculation. :) R. ... be carefull! Databases as MySQL or FirebIrd or Oracle have a buildin function DateDiff, but the result is different!! Our function delivers the age of a person in years, months, days. The other datediff function delivers years OR month OR days. So you can't use them to calculate the age of a person for example!! -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
On 11/14/2013 4:41 AM, Reimar Grabowski wrote: On Thu, 14 Nov 2013 07:19:56 +0100 Jürgen Hestermann juergen.hesterm...@gmx.de wrote: Am 2013-11-13 19:42, schrieb Reimar Grabowski: 1 julian year = 365.25 days of 86400 SI seconds each. Of course there are lots of other definitions for year but if FPC uses the julian one the value is exact and no approximation So the difference between 2007-01-01 12:00 and 2008-01-01 12:00 ist *not* one year? It is not one julian year. There is nothing like a year. As i said there are different definitions. If you talk about calendar year it's length changes and is therefor not a good measure of time and not used in science. right but this whole thread was started because someone wanted a calendar based datediff function which returns years, months and days... granted, they could have used SI units of 86400 sec/day and 365.25 day's per year (30.4375 days/month) to calculate the difference between their ending date and the current date in a continuous calculation but then looking at the calendar and counting the ones they could see would be different... start: 14 Nov 2013 end: 01 Aug 2018 days: 1721 1721 / 365.25 = 4.7118412047 years = 4 years 0.7118412047 * 365.25 = 260 days 260 / 30.4375 = 8.5420944559 months = 8 months 0.5420944559 = 30.4375 = 16.5 days (trunc) 4 years, 8 months, 16 days OR (round) 4 years, 8 months, 17 days FWIW: the routine we've been working on (with bug fix modifications) returns the same output as the above (from openoffice calc)... 2013-11-14 to 2018-08-01 is4 yrs8 mos 17 days yay! :lol: It's only 365,00 days and therefore not a full year according to your definition. Correct. And this is not my definition it is the correct definition of a julian year and it is based on SI units. Time is measured in SI seconds. If you cannot express 'your year' as seconds it is not a unit of time. by who's definition of time? ;) O:) But this it totaly wrong. Care to elaborate? Or is it just your gut feeling? Same day same time of one year and the next should always be a one year difference. According to what definition of year? Calendar year is a rather poor unit to measure time differences as it is not constant and cannot be expressed in seconds. actually, it can be but depending on the frame reference used, it is either fractions or the count varies ;) so far we have determined in this thread that there are at least four basic sets of routines... calendar inclusive calendar exclusive fixed inclusive (existing *Span routines) fixed exclusive (existing *Between routines) inclusive: includes the first and last days of the period in the count. used in (eg) rent and age calculations. eg: Mon 01 Jul 2013 - Fri 05 Jul 2013 = 5 day work week Mon 01 Jul 2013 - Sun 07 Jul 2013 = 7 day (1 week) rental exclusive: does not count the last day of the period. used in (eg) financial calculations. eg: Mon 01 Jul 2013 - Mon 08 Jul 2013 = 7 days calendar: the difference between the date in one year and the same date in the next or previous year is 1 year... the same with days in months... the 10th is one month from the 10th of the previous month and one month from the 10th in the next month no matter how many days there are in the months involved... fixed: SI oriented counting of the length of years, months and days using specific values for each... The average length of a year in days is: 346.62: a draconitic year 353, 354, 355 : common years in some lunisolar calendars 354.37: average length of a year in lunar calendars 365 : a vague year and a common year in many solar calendars 365.24219 : mean tropical year (rounded to 5 places) for epoch 2000 365.2424 : vernal equinox year (rounded to 4 places) for epoch 2000 365.2425 : average length of a year in the Gregorian calendar 365.25: the average length of a year in the Julian calendar 365.25636 : mean solar year 365.2564 : a sidereal year 365.25689 : a Gaussian year 366 : a leap year in many solar calendars 383, 384 385 : leap years in some lunisolar calendars. 383.9 : leap year in some lunisolar calendars. Astronomical years count the Julian year as a unit of time, defined as 365.25 days of 86400 SI seconds each with no leap seconds. A calendar year is an approximation of the Earth's orbital period in a given calendar. Gregorian calendar years (as well as in the Julian calendar) has either 365 (common years) or 366 (leap years) days. An average Gregorian year is 365.2425 days = 52.1775 weeks = 8765.82 hours = 525949.2 minutes = 31556952 seconds (mean solar, not SI). A common year is 365 days = 8760 hours = 525600 minutes = 31536000 seconds. A leap year is 366 days = 8784 hours = 527040 minutes = 31622400 seconds. The 400-year cycle of the Gregorian calendar has 146097 days and hence exactly 20871 weeks.
Re: [Lazarus] DateDif function needed
On 11/14/2013 4:50 AM, Reimar Grabowski wrote: On Wed, 13 Nov 2013 20:34:36 +0100 John Landmesser joh...@online.de wrote: What about Databases like mysql, Oracle, Firebird. I'm shure they have such a function. For MySQL: DATEDIFF(expr1,expr2) DATEDIFF() returns expr1 – expr2 expressed as a value in days from one date to the other. expr1 and expr2 are date or date-and-time expressions. Only the date parts of the values are used in the calculation. same thing as openOffice Calc... then, as i mention in my other post in this thread, one has to figure out how to count the years and months which will use either estimations (decimal fractions) or variants (actual numbers of days per month and year)... the big decision is which one to use for whatever accuracy is desired O:) -- NOTE: No off-list assistance is given without prior approval. Please keep mailing list traffic on the list unless private contact is specifically requested and granted. -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
On Thu, 14 Nov 2013 13:48:46 +0100 John Landmesser joh...@online.de wrote: [...] Our function delivers the age of a person in years, months, days. What is your diff between 31th Jan and 30 March 2013? Mattias -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
On 11/14/2013 7:25 AM, José Mejuto wrote: Maybe I'm completly wrong ? you are completely right, IMHO... one simply needs to choose their desired base and level of error that is acceptable for their task's needs... the initial problem arose because there's no easy way to calc the desired output with the existing routines and a lot of dancing about... spreadsheets and other languages are in the same boat, too, with the routines they offer... eg: openOffice Calc - no easy way to retain only the fraction of a result so one must dance with subtracting and truncating all the while recalculating the values over and over again... one can elect to use some scratchpad area on the sheet to store some intermittent values... witness: these formulas from Calc using fractional estimations like existing routines in FPc/Lazarus [without scratchpad] total days: =DAYS(A2;B2) whole years: =INT(C2/365.25) [C2 holds total days value] whole months: =INTC2/365.25)-TRUNC(C2/365.25))*365.25)/30.4375) whole days: =ROUND((C2/365.25)-TRUNC(C2/365.25))*365.25)/30.4375)-TRUNC(C2/365.25)-TRUNC(C2/365.25))*365.25)/30.4375)))*30.4375) [with scratchpad] end date: 08/01/2018 [MM/DD/ in A2] start date: 11/14/2013 [MM/DD/ in B2] days between: =DAYS(A2;B2)[in C2] 1721 real years: =C2/365.25 [in AD2] 4.7118412047 int years:=INT(AD2) [in D3] 4 real months: =((AD2-TRUNC(AD2))*365.25)/30.4375 [in AE2] 8.5420944559 int months: =INT(AE2) [in E2] 8 real days:=((AE2)-TRUNC(AE2))*30.4375[in AF2] 16.5 int days: =ROUND(AF2) [in F2] 17 -- NOTE: No off-list assistance is given without prior approval. Please keep mailing list traffic on the list unless private contact is specifically requested and granted. -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
On 14.11.2013 14:16, Mattias Gaertner wrote: On Thu, 14 Nov 2013 13:48:46 +0100 John Landmesser joh...@online.de wrote: [...] Our function delivers the age of a person in years, months, days. What is your diff between 31th Jan and 30 March 2013? Mattias -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus answer: Jedi DateDiff: 0 Year, 1 month, 30 days It's really difficult according to waldo kitty's post: today 14:10 * Hihi, i asked a question about a DateDiff function for FreePascal, because i wanted to know: how many years, month, days left to work in Office until my pension begins on 01.08.2018. .. and where are we now?? -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
Frankly, this list from time to time ... Em 14-11-2013 11:10, John Landmesser escreveu: On 14.11.2013 14:16, Mattias Gaertner wrote: On Thu, 14 Nov 2013 13:48:46 +0100 John Landmesser joh...@online.de wrote: [...] Our function delivers the age of a person in years, months, days. What is your diff between 31th Jan and 30 March 2013? Mattias -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus answer: Jedi DateDiff: 0 Year, 1 month, 30 days It's really difficult according to waldo kitty's post: today 14:10 * Hihi, i asked a question about a DateDiff function for FreePascal, because i wanted to know: how many years, month, days left to work in Office until my pension begins on 01.08.2018. .. and where are we now?? -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
On 11/14/2013 03:46 PM, Frederic Da Vitoria wrote: .. and where are we now?? Right in the middle of a very interesting discussion :-) -1 -Michael -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
On 11/14/2013 8:16 AM, Mattias Gaertner wrote: On Thu, 14 Nov 2013 13:48:46 +0100 John Landmesser joh...@online.de wrote: [...] Our function delivers the age of a person in years, months, days. What is your diff between 31th Jan and 30 March 2013? the one i am currently testing returns 2013-01-31 to 2013-03-30 is0 yrs1 mos 30 days FWTW, too ;) leapyear: 2012-01-31 to 2012-03-30 is0 yrs1 mos 30 days non-leapyear to leapyear: 2011-01-31 to 2012-03-30 is1 yrs1 mos 30 days leapyear to non-leapyear: 2012-01-31 to 2013-03-30 is1 yrs1 mos 30 days non-leapyear thru leapyear to non-leapyear: 2011-01-31 to 2013-03-30 is2 yrs1 mos 30 days leapyear thru non-leapyear to non-leapyear: 2012-01-31 to 2014-03-30 is2 yrs1 mos 30 days the whole of Feb is counted as a month no matter how many days it has... -- NOTE: No off-list assistance is given without prior approval. Please keep mailing list traffic on the list unless private contact is specifically requested and granted. -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
John Landmesser schrieb: Hihi, i asked a question about a DateDiff function for FreePascal, because i wanted to know: how many years, month, days left to work in Office until my pension begins on 01.08.2018. What do you consider as *one* year, month etc., fixed (average) values or calender values? When you get numbers for the years, months etc. remaining, and you reduce the number of days every day, what would you do when reaching zero days? You decrease months by one, and reset days to *which* amount? .. and where are we now?? Still before your answer. DoDi -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
2013/11/14 Michael Schnell mschn...@lumino.de On 11/14/2013 03:46 PM, Frederic Da Vitoria wrote: .. and where are we now?? Right in the middle of a very interesting discussion :-) -1 Well, everyone is entitled to his opinions, right, else we would all be doing C :-) -- Frederic Da Vitoria (davitof) Membre de l'April - « promouvoir et défendre le logiciel libre » - http://www.april.org -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
2013/11/14 John Landmesser joh...@online.de Hihi, i asked a question about a DateDiff function for FreePascal, because i wanted to know: how many years, month, days left to work in Office until my pension begins on 01.08.2018. .. and where are we now?? Right in the middle of a very interesting discussion :-) -- Frederic Da Vitoria (davitof) Membre de l'April - « promouvoir et défendre le logiciel libre » - http://www.april.org -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
On 11/14/13, waldo kitty wkitt...@windstream.net wrote: you are completely right, IMHO... one simply needs to choose their desired base and level of error that is acceptable for their task's needs... It's all about definition. For me I would think that given today is the last day of a given month, then today + 1 month = the same date on in the next month, or if the next month has fewer day, the last day of the next month. So - april 30th + 1 month = may 30th - march 31st + 1 month = may 30th (not june 1st) Yet all of our tools (includimg mine) say march 31st to april 30th = 0 months + 30 days... Bart -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
Am 2013-11-14 07:56, schrieb Patrick Chevalley: So the difference between 2007-01-01 12:00 and 2008-01-01 12:00 ist *not* one year? No, the base definition of the year is not a digit change, but the time it take to the Earth to return at the same point of its orbit around the Sun. Well, *this* value (earth at the same point) is also varying. When doing astronomical calculations I would definitely not use a fixed value. The julian year of 365.25 is a convenient approximation still in use despite the julian calendar was abrogated some 400 years ago. Of what use would it be to use 365.25 days as a representation of a year? You can also use 400 instead. It would be just an arbitrary definition decoupled from calendars. You cannot calculate anything useful with it. Neither calendar dates nor astronomical things. It is just an accademic value and exists only because it is so easy to use. All this efforts are to bypass the problem with the calendar year (the one you mention) because it is sometime 365 and sometime 366 days. This is a totally unacceptable definition when you need an homogeneous time scale. Well, that's just the whole point of this thread: The time scale we are talking about here is *not* homogeneous! Instead, a synchronization with calendar dates is wanted/needed. That has always been a problem with calendar definitons. The rotation of earth around the sun is not a whole-numbered multiple of its rotation around itself but we want a whole number of days (otherwise day time would no longer be related to sunlight). So we synchronize our calendar with the run of the sun by leap days (and leap seconds). But now years and months are no longer a fixed value. Therefore differences must be calculated in a more complex way based on dates and not as a fixed number of (milli)seconds. It's easy to use fixed values for day, month, year but it is of no use when talking about calendars. So all depend of the use you need for your application and it must be admitted that one set of definition/function is not sufficient and every one must be careful when using time period. Just give me an example where a fixed value for a month is of use? If you rent an appartement you will definitely not be able to insist on your fixed definition of a month (i.e., when starting on february the 1st). In daily usage the time ranges vary depending on the month you look at. For me the very simple functions as implemented if FPC are sufficient, In what context do you use these functions? -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
On 11/14/2013 12:26 PM, Bart wrote: On 11/14/13, waldo kitty wkitt...@windstream.net wrote: you are completely right, IMHO... one simply needs to choose their desired base and level of error that is acceptable for their task's needs... It's all about definition. right... that's what i meant by desired base... eg: calendar, SI notation, Julian, Gregorian, etc...) For me I would think that given today is the last day of a given month, then today + 1 month = the same date on in the next month, agreed... or if the next month has fewer day, the last day of the next month. yeah... i'm undecided on that :? (** below) my current code returns the following... 2012-01-29 to 2012-02-29 is 0 yrs 1 mos 0 days 2012-01-29 to 2012-03-01 is 0 yrs 1 mos 3 days 2012-01-29 to 2012-03-31 is 0 yrs 2 mos 2 days 2012-01-29 to 2012-04-30 is 0 yrs 3 mos 1 days 2012-01-29 to 2012-05-31 is 0 yrs 4 mos 2 days 2012-01-29 to 2012-06-30 is 0 yrs 5 mos 1 days 2012-01-29 to 2012-07-31 is 0 yrs 6 mos 2 days 2012-01-29 to 2012-08-31 is 0 yrs 7 mos 2 days 2012-01-29 to 2012-09-30 is 0 yrs 8 mos 1 days 2012-01-29 to 2012-10-31 is 0 yrs 9 mos 2 days 2012-01-29 to 2012-11-30 is 0 yrs 10 mos 1 days 2012-01-29 to 2012-12-31 is 0 yrs 11 mos 2 days 2012-01-31 to 2012-02-29 is 0 yrs 0 mos 29 days** 2012-01-31 to 2012-03-01 is 0 yrs 1 mos 1 days 2012-01-31 to 2012-03-31 is 0 yrs 2 mos 0 days 2012-01-31 to 2012-04-30 is 0 yrs 2 mos 30 days** 2012-01-31 to 2012-05-31 is 0 yrs 4 mos 0 days 2012-01-31 to 2012-06-30 is 0 yrs 4 mos 30 days** 2012-01-31 to 2012-07-31 is 0 yrs 6 mos 0 days 2012-01-31 to 2012-08-31 is 0 yrs 7 mos 0 days 2012-01-31 to 2012-09-30 is 0 yrs 7 mos 30 days** 2012-01-31 to 2012-10-31 is 0 yrs 9 mos 0 days 2012-01-31 to 2012-11-30 is 0 yrs 9 mos 30 days** 2012-01-31 to 2012-12-31 is 0 yrs 11 mos 0 days So - april 30th + 1 month = may 30th - march 31st + 1 month = may 30th (not june 1st) Yet all of our tools (includimg mine) say march 31st to april 30th = 0 months + 30 days... i know what you mean ;) :) -- NOTE: No off-list assistance is given without prior approval. Please keep mailing list traffic on the list unless private contact is specifically requested and granted. -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] DateDif function needed
On 11/14/2013 12:48 PM, Jürgen Hestermann wrote: Am 2013-11-14 07:56, schrieb Patrick Chevalley: So the difference between 2007-01-01 12:00 and 2008-01-01 12:00 ist *not* one year? No, the base definition of the year is not a digit change, but the time it take to the Earth to return at the same point of its orbit around the Sun. Well, *this* value (earth at the same point) is also varying. exactly! the earth does not travel in a perfect circle around the sun with the sun in a fixed central position... then there's the tilt of the earth and that the poles wobble around following the 25770 year equinox precession such that Deneb will be the north pole star instead of Polaris at some point in the future (AD1) :) When doing astronomical calculations I would definitely not use a fixed value. but many do use fixed fractional average numbers to make the math easier and they live with the small errors... witness my long posting earlier today with the charts of days per year values and the numerous year periods ;) The julian year of 365.25 is a convenient approximation still in use despite the julian calendar was abrogated some 400 years ago. Of what use would it be to use 365.25 days as a representation of a year? You can also use 400 instead. It would be just an arbitrary definition decoupled from calendars. You cannot calculate anything useful with it. Neither calendar dates nor astronomical things. It is just an accademic value and exists only because it is so easy to use. i can agree with this ;) All this efforts are to bypass the problem with the calendar year (the one you mention) because it is sometime 365 and sometime 366 days. This is a totally unacceptable definition when you need an homogeneous time scale. Well, that's just the whole point of this thread: The time scale we are talking about here is *not* homogeneous! Instead, a synchronization with calendar dates is wanted/needed. That has always been a problem with calendar definitons. The rotation of earth around the sun is not a whole-numbered multiple of its rotation around itself but we want a whole number of days (otherwise day time would no longer be related to sunlight). So we synchronize our calendar with the run of the sun by leap days (and leap seconds). But now years and months are no longer a fixed value. Therefore differences must be calculated in a more complex way based on dates and not as a fixed number of (milli)seconds. It's easy to use fixed values for day, month, year but it is of no use when talking about calendars. i couldn't have said it better :) So all depend of the use you need for your application and it must be admitted that one set of definition/function is not sufficient and every one must be careful when using time period. Just give me an example where a fixed value for a month is of use? If you rent an appartement you will definitely not be able to insist on your fixed definition of a month (i.e., when starting on february the 1st). In daily usage the time ranges vary depending on the month you look at. one can see this in recurring billings... some are 30 billing periods whereas others are monthly based where the bill is due on the same day of each month... in the former case, the due date floats about in each successive month... the latter is always on the X day of the month... i much prefer monthly billing over 30 day billing ;) For me the very simple functions as implemented if FPC are sufficient, In what context do you use these functions? -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus -- NOTE: No off-list assistance is given without prior approval. Please keep mailing list traffic on the list unless private contact is specifically requested and granted. -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
