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Paper 068-29
Dating SAS® and MS Excel
Erik W. Tilanus, independent consultant, Vinkeveen, the Netherlands ABSTRACT
Exchanging formatted date and time values between SAS and Excel may appear problematic, since the formats do
not always match. Using local language versions of Excel can aggravate the problems. Internally both SAS and
Excel use a numeric representation of dates and times. However they differ in anchor point (day 0) and in method.
Using the internal structure, problems can be avoided, although a relatively simple transformation is required.
INTRODUCTION
There are several options to exchange data between SAS and Excel. The PC-File formats interface can read and
create spreadsheets directly. If you do not have that option installed, a simple and effective method is to exchange
data using tab-separated or comma separated values files. In general this works fine, except that dates, times and
date/time combinations can cause troubles because of the different format specifications used by SAS and Excel.
This is more so if you are using localized versions in different languages.
In this paper we show how to avoid those problems, by exchanging non-formatted (internal) dates, times and
date/time values.
INTERNAL REPRESENTATION OF DATES AND TIMES
As generally known, a SAS date is a simple numeric value internally: the number of days since 1 January 1960.
1 January 1960 is day zero. Dates before this reference date have a negative internal value and the calendar is
correct back to the 16th century and into the future for many centuries to come.
Times are counted internally in SAS as seconds since midnight and date/time combinations are calculated as thenumber of seconds since midnight 1 January 1960.
Excel also uses simple numerical values for dates and times internally. For the date values the difference with the
SAS date is only the anchor point. Excel uses 1 January 1900 as day one.
Times are represented somewhat differently in Excel: a time in Excel is a fraction of a day. So for instance 12:00noon in SAS is 43200 (seconds since midnight), in Excel it is 0.5 (half day).
This fraction approach is also used in date/time combinations. The integer part of the date/time combination is equalto the single date value. The fraction adds the time on the day.
CONVERSION FROM EXCEL TO SAS
With the knowledge of the internal values of Excel and SAS dates conversion is simple.
If you want to convert from an Excel date to a SAS date, subtract 21916: the difference in the starting points of the
calendars.
Conversion of an Excel time value into a SAS time value is a question of multiplying by 86400, the number of
seconds in a day.
Conversion of a date/time value is hardly more complicated: correct the date part by subtracting 21916 and then
multiply the results by 86400 to convert it to the seconds used in SAS date/time values.
EXAMPLES:
SAS_date = Excel_date - 21916;SAS_time = Excel_time * 86400;SAS_date_time = (Excel_date_time - 21916) * 86400; CONVERSION FROM SAS TO EXCEL
The other way around is obvious: reverse the calculations used in the previous paragraph. The examples are self-
explanatory.
EXAMPLES:
Excel_date = SAS_date + 21916;Excel_time = SAS_time / 86400;Excel_date_time = SAS_date_time / 86400 + 21916; NEGATIVE DATE VALUES
There is one major difference between SAS and Excel dates and times: a SAS date, time or date/time value can also
be negative. In Excel this is impossible. If you enter day 0, it will display as "0 January 1900"! A negative value
creates an error display (############)
The same happens with time values.
TIME VALUES HIGHER THAN 24 HOURS
Also note that the default format for times in Excel is HH:MM<:SS>. But HH does not go over 24 by default. So 15:00
+ 16:00 displays as 7:00, unless you change the cell format!
DEMONSTRATION
Figure 1 shows a part of an Excel spreadsheet with various date and date/time values, according to default
formatting (column A,D,G), their unformatted values (column B,E) and their conversion to the corresponding SAS
value (column C,F). Column H shows the difference of D2 and G2: a positive value, formatted as time, with next to it
the unformatted value. Note that the real difference should be 46:40:00! Column J and K show what happens if you
subtract D2 from G2: a negative value.
Figure 1: an Excel spreadsheet with a number of date and date time values, formatted and unformatted and theirconversion to SAS values. Figure 2 shows what the result is when you save this spreadsheet as a comma separated values (CSV) file.
Standard Excel date,Same - unformatted,Converted unformatted date (=B2-21916),StandardDate/time value,Unformatted date/time value,Converted date time value (=E2-21916)*86400),Second date/time value,"Difference between date/time values (=D2-G2),HH:MM:SS format)",Unformatted difference between date time values,"Difference betweendate/time values =D2-G2), HH:MM:SS format)",Unformatted difference between date timevalues9-May-04,38116,16200,12/5/2004 8:10,38119.34028,1399968600,10/5/20049:30,22:40:00,1.944444444,###############################################################################################################################################################################################################################################################,-1.944444444Figure 2: A CSV file version of the spreadsheet. The easy way to read this CSV file is by using the IMPORT DATA wizard from the file menu in the display manager.
However the result will not be satisfactory: it will not recognize several of the formats and it will create duplicatevariable names for columns H to K. But still it is useful to run the wizard and then recall the generated source toadapt it to your own needs. This may be changing the format or informat specifications, the variable names or anyother change or addition to the generated DATA step. In this example the modified source looks as follows: data WORK.date_time_values;
infile 'C:\SUGI29\date-time examples.csv' delimiter = ',' MISSOVER DSD lrecl=32767 firstobs=2 ;
informat Same_unformatted best32. ;informat Converted_unformatted_date best32. ;informat Standard_Date_time_value anydtdtm. ; informat Unformatted_date_time_value best32. ;informat Converted_date_time_value best32. ;informat Second_date_time_value anydtdtm. ; informat Difference_between_DT_pos anydttme. ; informat Unformatted_difference_DT_pos best32. ;informat VAR10 $255. ;informat Unformatted_difference_DT_neg best32. ; format Standard_Excel_date date9. ;format Same_unformatted best12. ;format Converted_unformatted_date date9. ;format Standard_Date_time_value datetime. ;format Unformatted_date_time_value best12. ;format Converted_date_time_value datetime. ;format Second_date_time_value datetime. ;format Difference_between_DT_pos time. ;format Unformatted_difference_DT_pos best. ;format Converted_difference_DT_pos time.;format VAR10 $20.;format Unformatted_difference_DT_neg best. ;format Converted_difference_DT_neg time.;input Standard_Excel_dateSame_unformattedConverted_unformatted_dateStandard_Date_time_valueUnformatted_date_time_valueConverted_date_time_valueSecond_date_time_valueDifference_between_DT_posUnformatted_difference_DT_posVAR10Unformatted_difference_DT_neg Converted_difference_DT_pos = Unformatted_difference_DT_pos*86400;
Converted_difference_DT_neg = Unformatted_difference_DT_neg*86400;
The PUT statements generate the following information in the SAS LOG: Standard_Excel_date=09MAY2004Same_unformatted=38116Converted_unformatted_date=09MAY2004Standard_Date_time_value=.
Unformatted_date_time_value=38119.34028Converted_date_time_value=12MAY04:08:10:00Second_date_time_value=.
Difference_between_DT_pos=22:40:00Unformatted_difference_DT_pos=1.944444444VAR10=####################Unformatted_difference_DT_neg=-1.944444444Converted_difference_DT_pos=46:40:00Converted_difference_DT_neg=-46:40 From these results you can derive that the formatted date/time values are not read in correctly. The other input fieldsare read smoothly and with the proper conversion on the Excel side or on the SAS side the resulting values arecorrect.
CONCLUSION
Converting SAS date, time and date/time values into the Excel equivalent or vice versa is easy. However be aware of
some limitations in the date and time handling in Excel.
CONTACT INFORMATION
Your comments and questions are valued and encouraged. Contact the author at:
Erik W. TilanusPO Box 773645 ZK Vinkeveenthe NetherlandsPhone: +31 297 263936Fax: SAS and all other SAS Institute Inc. product or service names are registered trademarks or trademarks of SASInstitute Inc. in the USA and other countries. ® indicates USA registration.
Other brand and product names are trademarks of their respective companies.

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