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# Julian dates question

 P: n/a How may I represent dates as Julian dates - I have seen code where julian dates are represented as longs, and other where they are represented as floats. Which is the correct representation? Anyone knows where I can obtain a routine for converting: 1). Dates to/from julian representations 2). Date/time values to/from Julian representations Jul 13 '06 #1
4 Replies

 P: n/a How may I represent dates as Julian dates - I have seen code where julian dates are represented as longs, and other where they are represented as floats. Which is the correct representation? Anyone knows where I can obtain a routine for converting: 1). Dates to/from julian representations 2). Date/time values to/from Julian representations I don't think there is a direct way, but see the various properties of DateTime and TimeSpan. I think you can build it. DateTime.DayOfYear to get the daynumber. With a timespan (DateTime.Now - DateTime.Today) you can also get the TotalMinutes (or smaller). You can use AddDays to add any number of days to a given date. Hans Kesting Jul 13 '06 #2

 P: n/a I am a complete C# newbie, so I may be misunderstanding Hans' post, but I wanted to point out something: A Julian date is actually the number of days (and fractional days) since noon Jan. 1, 4713 BC. Many people in the I.T. community for some reason call a date "Julian" when it simply counts the number of days from the beginning of the year. For instance, 7/13/2006 is sometimes represented in systems that lack a date datatype as 2006193 (the 193rd day of 2006) I do not know the proper term for this representation of a date, but it isn't a Julian date. I think Han's method is geard toward this later representation. Thanks, Mac "Hans Kesting" How may I represent dates as Julian dates - I have seen code where juliandates are represented as longs, and other where they are represented asfloats. Which is the correct representation?Anyone knows where I can obtain a routine for converting:1). Dates to/from julian representations2). Date/time values to/from Julian representations I don't think there is a direct way, but see the various properties of DateTime and TimeSpan. I think you can build it. DateTime.DayOfYear to get the daynumber. With a timespan (DateTime.Now - DateTime.Today) you can also get the TotalMinutes (or smaller). You can use AddDays to add any number of days to a given date. Hans Kesting Jul 14 '06 #3

 P: n/a Bit byte wrote: How may I represent dates as Julian dates - I have seen code where julian dates are represented as longs, and other where they are represented as floats. Which is the correct representation? Anyone knows where I can obtain a routine for converting: 1). Dates to/from julian representations 2). Date/time values to/from Julian representations the routine is basicly this: long DateToJulian(int y, int m, int d) { return (1461 * (y + 4800 + (m - 14) / 12)) / 4 + (367 * (m - 2 - 12 * ((m - 14) / 12))) / 12 - (3 * ((y + 4900 + (m - 14) / 12) / 100)) / 4 + d - 32075; } I found it on the web some time ago. Needed it in a lowlevel C app once. In .NET you don't really need it, as DateTime has all you need :) FB -- ------------------------------------------------------------------------ Lead developer of LLBLGen Pro, the productive O/R mapper for .NET LLBLGen Pro website: http://www.llblgen.com My .NET blog: http://weblogs.asp.net/fbouma Microsoft MVP (C#) ------------------------------------------------------------------------ Jul 14 '06 #4

 P: n/a See http://www.vsg.cape.com/~pbaum/date/back.htm mac wrote: I am a complete C# newbie, so I may be misunderstanding Hans' post, but I wanted to point out something: A Julian date is actually the number of days (and fractional days) since noon Jan. 1, 4713 BC. Many people in the I.T. community for some reason call a date "Julian" when it simply counts the number of days from the beginning of the year. For instance, 7/13/2006 is sometimes represented in systems that lack a date datatype as 2006193 (the 193rd day of 2006) I do not know the proper term for this representation of a date, but it isn't a Julian date. I think Han's method is geard toward this later representation. Thanks, Mac "Hans Kesting" >>How may I represent dates as Julian dates - I have seen code where juliandates are represented as longs, and other where they are represented asfloats. Which is the correct representation?Anyone knows where I can obtain a routine for converting:1). Dates to/from julian representations2). Date/time values to/from Julian representations I don't think there is a direct way, but see the various properties ofDateTime and TimeSpan. I think you can build it.DateTime.DayOfYear to get the daynumber.With a timespan (DateTime.Now - DateTime.Today) you can also get theTotalMinutes (or smaller).You can use AddDays to add any number of days to a given date.Hans Kesting Jul 14 '06 #5

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