[EpiData-list] How to handle dates in analysis

epidata-list at lists.umanitoba.ca epidata-list at lists.umanitoba.ca
Sun Mar 11 04:15:22 CDT 2007

Neither EpiData Entry nor EpiData Analysis can have date fields with
illegal dates. E.g. February 29th is only allowed in leap years.

Epi6 could save illegal dates and never controlled the data while reading
for correct content.

>From the beginning of EpiData all date fields were included as "true
dates", meaning that there cannot be a date value which does not exist in
the past or future. (dates before year 1600 can give problems)

For EpiData Analysis this has given some users problems since it was
difficult to see in which records the date problems were located if some
dates were rejected. Also some old dates before year 1800 have not been
accomodated fully in analysis, but this should be a minor problem, since
we never or very rarely have data from that period. And if we do one could
split the dates into day month and year parts as three variables, although
this would remove the automatic validation of the content of the data.

I suggest that we look at the possibility of implementing:
> c.  That, if neither a. nor b. is an option, more detail about the
> 'invalid' dates (record number, variable name) is provided so that
> they can be edited.

since we cannot use an illegal date for anything. Analysis with incorrect
dates makes no sense.

Once we find a workable principle for this the same technical principle
and list can include also names of variables/fields, which will be in
conflict with internal functions, e.g. year, date or tab.

Jens Lauritsen
Coordinator and initiator of EpiData Project

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