Dates and times

Formats

There are three common formats across SAS, SPSS and Stata.

Date (number of days)

• SAS: MMDDYY, DDMMYY, YYMMDD, DATE
• Spss: n/a
• Stata: %td

Time (number of seconds):

• SAS: TIME, HHMM, TOD
• Spss: TIME, DTIME
• Stata: n/a

DateTime (number of seconds):

• SAS: DATETIME
• Spss: DATE, ADATE, SDATE, DATETIME (as milliseconds)
• Stata: %tc, %tC

Offsets

Dates and date times use a difference offset to R:

• SAS: 1960-01-01 (3653 days)
• Spss: 1582-10-14. (141428 days)
• Stata: 1960-01-01. (3653 days)

References

• SAS: https://v8doc.sas.com/sashtml/lrcon/zenid-63.htm, http://support.sas.com/documentation/cdl/en/etsug/60372/HTML/default/viewer.htm

• Spss: http://www-01.ibm.com/support/knowledgecenter/#!/SSLVMB_20.0.0/com.ibm.spss.statistics.help/idh_idd_dtwz_learn.htm http://www-01.ibm.com/support/knowledgecenter/#!/SSLVMB_20.0.0/com.ibm.spss.statistics.help/syn_date_and_time_date_time_formats.htm

• Stata: http://www.stata.com/manuals13/u24.pdf