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General Programming » Date and Time » General     Intermediate License: The Common Development and Distribution License (CDDL)

Excel serial date to Day, Month, Year and vise versa

By Victor Vogelpoel

A speedy algorithm to convert Excel numbers to DMY and vise versa.
VC6, VC7Win2K, WinXP, Visual Studio, Dev
Posted:12 Aug 2002
Views:168,879
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19 votes for this article.
Popularity: 5.86 Rating: 4.59 out of 5

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Introduction

For a little project of mine, I needed to convert a serial date number to day/month/year (DMY) and vise versa. The serial number came from date field in a converted Paradox database and seemed to be exactly the same as the serial date in Microsoft Excel, hence the article name. After some googling I learned that the Excel serial date is related to Julian date, and found a speedy algorithm to convert these numbers to DMY and vise versa.

Excel Serial Date Number

Now what is an Excel serial date number? 37477 is a serial date number and is the number of days since 1-1-1900. 37477 actually translates to Aug 9, 2002, the date of writing this article.

The number of days since 1-1-1900 isn't that hard to calculate of course, once you know the leap years. Microsoft Excel however contains a bug with its date calculation: it considers 29-02-1900 as a valid date, but 1900 isn't a leap year! 29-02-1900 is not a valid date!

According to the stories, Microsoft decided to duplicate this date bug from Lotus 123, which was the dominating spreadsheet application at the time Excel was being written. This allowed Excel to open Lotus 123 spreadsheets without date problems.

(Note that a serial date number may also contain a fraction that denotes the time. It's actually the percentage of 24 hours, but that's not for this article.)

Mac Excel Serial Date number

Excel on the Apple Mac uses a slightly different Serial Date number base: the number of days since 1-1-1904. That's why Excel also features a "1904 Date System" checkbox in its Options (Calculation tab). I won't go into this futher.

Translating Serial Date Number to DMY

First of all, credit where credit is due. I got the basic algorithm from http://serendipity.magnet.ch/hermetic/cal_stud/jdn.htm. It's about converting a Julian date to DMY using integer calculations. I won't bore you with the theory (following the above hyperlink), but the original Julian has a different base date.

With an addition of a certain number, the algorithm comes close to the Excel serial date. And when the 29-02-1900 issue is handled, we've got an Excel serial date to Day, Month, Year calculation!

void ExcelSerialDateToDMY(int nSerialDate, int &nDay, 
                          int &nMonth, int &nYear)
{
    // Excel/Lotus 123 have a bug with 29-02-1900. 1900 is not a

    // leap year, but Excel/Lotus 123 think it is...

    if (nSerialDate == 60)
    {
        nDay    = 29;
        nMonth    = 2;
        nYear    = 1900;

        return;
    }
    else if (nSerialDate < 60)
    {
        // Because of the 29-02-1900 bug, any serial date 

        // under 60 is one off... Compensate.

        nSerialDate++;
    }

    // Modified Julian to DMY calculation with an addition of 2415019

    int l = nSerialDate + 68569 + 2415019;
    int n = int(( 4 * l ) / 146097);
            l = l - int(( 146097 * n + 3 ) / 4);
    int i = int(( 4000 * ( l + 1 ) ) / 1461001);
        l = l - int(( 1461 * i ) / 4) + 31;
    int j = int(( 80 * l ) / 2447);
     nDay = l - int(( 2447 * j ) / 80);
        l = int(j / 11);
        nMonth = j + 2 - ( 12 * l );
    nYear = 100 * ( n - 49 ) + i + l;
}

DMY to Excel Serial Date

Calculate an Excel serial date from Day, Month, Year. The function assumes that the day, month and year are valid date numbers.

int DMYToExcelSerialDate(int nDay, int nMonth, int nYear)
{
    // Excel/Lotus 123 have a bug with 29-02-1900. 1900 is not a

    // leap year, but Excel/Lotus 123 think it is...

    if (nDay == 29 && nMonth == 02 && nYear==1900)
        return 60;

    // DMY to Modified Julian calculatie with an extra substraction of 2415019.

    long nSerialDate = 
            int(( 1461 * ( nYear + 4800 + int(( nMonth - 14 ) / 12) ) ) / 4) +
            int(( 367 * ( nMonth - 2 - 12 * ( ( nMonth - 14 ) / 12 ) ) ) / 12) -
            int(( 3 * ( int(( nYear + 4900 + int(( nMonth - 14 ) / 12) ) / 100) ) ) / 4) +
            nDay - 2415019 - 32075;

    if (nSerialDate < 60)
    {
        // Because of the 29-02-1900 bug, any serial date 

        // under 60 is one off... Compensate.

        nSerialDate--;
    }

    return (int)nSerialDate;
}

License

This article, along with any associated source code and files, is licensed under The Common Development and Distribution License (CDDL)

About the Author

Victor Vogelpoel


Member
Victor is consulting in The Netherlands.

His interests include Windows and web application development using .NET technologies and even some Apache/PHP/MySQL...
Occupation: Web Developer
Location: Netherlands Netherlands

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 Msgs 1 to 25 of 32 (Total in Forum: 32) (Refresh)FirstPrevNext
GeneralThanks. Pinmembersriest11:01 10 Jul '09  
GeneralHi. Thanks for the invaluable contribution. I have found a bug.... PinmemberMember 40217977:57 18 Nov '08  
NewsError in Excel Serial Date to DMY ?? PinmemberHarry Adams18:33 17 Sep '08  
GeneralPorted to PHP and fixed PinmemberLubosdz1:19 9 Aug '07  
QuestionWorks great for date, what about for time? PinmemberTariAbay21:19 29 Jul '07  
GeneralYEAR Pinmembergtown75:20 17 May '07  
GeneralGoing off after Febuvary... Pinmembervijaicmo1:23 12 Mar '07  
GeneralBut how can I know if the cell value is a Date? Pinmemberstanley guan17:51 7 Oct '05  
GeneralRe: But how can I know if the cell value is a Date? PinmemberVictor Vogelpoel23:56 7 Oct '05  
GeneralRe: But how can I know if the cell value is a Date? PinmemberSuunil3:21 21 Aug '09  
GeneralRe: But how can I know if the cell value is a Date? PinmemberVictor Vogelpoel0:51 24 Aug '09  
GeneralNumber off by 183 PinsussAnonymous5:33 29 Aug '05  
GeneralRe: Number off by 183 PinsussAnonymous7:03 29 Aug '05  
GeneralDMYToExcelSerialDate doesn't work for 28th Feb 1900 Pinmembercrusby0:09 10 Feb '05  
GeneralRe: DMYToExcelSerialDate doesn't work for 28th Feb 1900 PinmemberVictor Vogelpoel11:10 10 Feb '05  
Generaldoesn't work in months input > 12 PinsussAnonymous13:23 24 Jun '04  
GeneralRe: doesn't work in months input > 12 PinmemberVictor Vogelpoel23:54 24 Jun '04  
GeneralThanks - Would like some clarifications Pinmemberjocompto10:11 4 May '04  
GeneralRe: Thanks - Would like some clarifications PinmemberVictor Vogelpoel11:29 4 May '04  
Generaldate month year in excel PinsussAnonymous5:36 3 May '04  
GeneralRe: date month year in excel PinmemberVictor Vogelpoel9:44 3 May '04  
GeneralDifferent Results then Excel PinsussAlex Baldini13:14 20 Oct '03  
GeneralPorted to PHP PinsussNathan Gasser17:39 24 Aug '03  
GeneralExcel dates in C# PinsussKris Vandermotten2:30 3 Apr '03  
GeneralRe: Excel dates in C# PinmemberVictor Vogelpoel8:41 3 Apr '03  

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Last Updated: 12 Aug 2002
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