assign value to a date?

[clickwhistle]

I am working with a spread sheet that has some dates in it which are unknown, these dates are noted as either ??-???-2010 (dd-mmm-yyyy) for those where only the year is known, or ??-Jan-2010 where the day is not known

Is there a way to assign a value to these odd date formats so they sort correctly? For example, in the case where only the year is known assignment of the values 00-000-yyyy would be helpful.

Anyone have an idea how to do this?

 

[clickwhistle]

Thanks for the help, I'll try those