Strategy for Incomplete Dates

Question

Working on an application where we would like the user to be able to enter incomplete dates.

In some cases there will only be a year - say 1854, or there might be a year and a month, for example March 1983, or there may be a complete date - 11 June 2001.

We'd like a single 'date' attribute/column - and to be able to sort on date.

Any suggestions?

Answer 1

Store the date as an integer -- yyyymmdd.

You can then zero out any month or day component that has not been entered

Year only: 1954 => 19540000
Year & Month: April 2004 => 20040400
January 1st, 2011 => 20110101

Of course I am assuming that you do not need to store any time of day information.

You could then create a struct to encapsulate this logic with useful properties indicating which level of granularity has been set, the relevant System.DateTime, etc

Edit: sorting should then work nicely as well

Answer 2

I can't think of a good way of using a single date field.

A problem you would get if you used January as the default month and 1 as the default day like others have suggested is, what happens when they actually pick January? How would you track if it's a selected January or a defaulted January.

I think you're going to have to store a mask along with the date. You would only need a bit per part of the date, which would only be 6 bits of data.

M|D|Y|H|Min|S

Month Only 1|0|0|0|0|0 = 32

Year Only 0|0|1|0|0|0 = 8

Month+Year 1|0|1|0|0|0 = 40

AllButMinSec 1|1|1|1|0|0 = 60

You could put this into a Flag Enum to make it easier to use in code.