# 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://support.sas.com/documentation/cdl/en/lrcon/65287/HTML/default/viewer.htm#p1wj0wt2ebe2a0n1lv4lem9hdc0v.htm

- SPSS: https://www.ibm.com/docs/en/spss-statistics/29.0.0?topic=wizard-dates-times-in-spss-statistics https://www.ibm.com/docs/en/spss-statistics/29.0.0?topic=formats-date-time

- Stata: https://www.stata.com/manuals/u25.pdf