calculate number of days since Jan 1, 0000

B

Beemer Biker

I cant seem to get that date into any DateTime to make my calculation
directly by subtracting "01-01-0000" from "now".

After reading this:
http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=11469&objectType=File

I kluged up this routine that works:
// convert date time into that funny matlab serial date time that starts at
jan 1, 0000
private string DT2Matlab(DateTime thisDT)
{
DateTime y1970 = Convert.ToDateTime("JAN-1-1970");
thisDT = thisDT.AddDays(719529);
// supposidly 719529 days from "0 CE" to 1970
TimeSpan ts = thisDT.Subtract(y1970);
return ts.TotalDays.ToString("#.####");
}

Seems there should be a cleaner way to calculate "Days.fraction_of_days"
from "0 CE" all in one swoop? "01-01-0001" gives the wrong answer when
subtracting and the 0000 is a no go.

...thanks for looking..


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Joseph "Beemer Biker" Stateson
http://TipsForTheComputingImpaired.com
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P

PS

Beemer Biker said:
I cant seem to get that date into any DateTime to make my calculation
directly by subtracting "01-01-0000" from "now".

After reading this:
http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=11469&objectType=File

I kluged up this routine that works:
// convert date time into that funny matlab serial date time that starts
at jan 1, 0000
private string DT2Matlab(DateTime thisDT)
{
DateTime y1970 = Convert.ToDateTime("JAN-1-1970");
thisDT = thisDT.AddDays(719529);
// supposidly 719529 days from "0 CE" to 1970
TimeSpan ts = thisDT.Subtract(y1970);
return ts.TotalDays.ToString("#.####");
}

Seems there should be a cleaner way to calculate "Days.fraction_of_days"
from "0 CE" all in one swoop? "01-01-0001" gives the wrong answer when
subtracting and the 0000 is a no go.
Click to expand...

Just factor in the extra days that you need when you use DateTime.MinValue
in your method. Why don't you give us a specific date and the number that
you want to see as representing that date?

PS
 
A

Alun Harford

Beemer said:
I cant seem to get that date into any DateTime to make my calculation
directly by subtracting "01-01-0000" from "now".

After reading this:
http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=11469&objectType=File


I kluged up this routine that works:
// convert date time into that funny matlab serial date time that starts
at jan 1, 0000
private string DT2Matlab(DateTime thisDT)
{
DateTime y1970 = Convert.ToDateTime("JAN-1-1970");
thisDT = thisDT.AddDays(719529);
// supposidly 719529 days from "0 CE" to 1970
TimeSpan ts = thisDT.Subtract(y1970);
return ts.TotalDays.ToString("#.####");
}

Seems there should be a cleaner way to calculate "Days.fraction_of_days"
from "0 CE" all in one swoop? "01-01-0001" gives the wrong answer when
subtracting and the 0000 is a no go.
Click to expand...

As has been said, there is no year 0, just as there is no month 0.

You might also want to be very careful about calendars - we've skipped
days in the past when calendars used were changed.

Alun Harford
 
B

Beemer Biker

Alun Harford said:
As has been said, there is no year 0, just as there is no month 0.
Click to expand...

Thanks Alun! I read where the year "0" is just a reference point, as
explained here: http://tinyurl.com/39b9es

quoteing "datenum is one of three conversion functions that enable you to
express dates and times in any of three formats in MATLAB: a string (or date
string), a vector of date and time components (or date vector), or as a
numeric offset from a known date in time (or serial date number). Here is an
example of a date and time expressed in the three MATLAB formats:

Date String: '24-Oct-2003 12:45:07'
Date Vector: [2003 10 24 12 45 07]
Serial Date Number: 7.3188e+005

A serial date number represents the whole and fractional number of days from
a specific date and time, where datenum('Jan-1-0000 00:00:00') returns the
number 1. (The year 0000 is merely a reference point and is not intended to
be interpreted as a real year in time.)"

I was looking for a clean (??) C# function to calculate that 7.3188e+005
Googleing I found a UTC -> Matlab that used 1970. I thought there might be
a clean way to get the time span in days.fraction_of_days out of the
DateTime function. What I have works, though it is probably not accurate
by "days in the past" let alone leap-seconds. I have a C# program that
generates a text file that is being used as input to a matlab program. The
engineer wants time in that funny number that matlab uses and was not happy
when I put out a date time string accurate down into milliseconds.
 
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