title: What is a good strategy, other than NULLs, for dealing with unknown datetime values?
body: <p>My database has 3 tables: Organization, User &amp; OrganizationUserJunction. The OrganizationUserJunction table tracks which organization a user belongs to, when they became a member of the organization, and when they left the organization. The MemberFrom field is populated with a known date but the MemberTo date is unknown at first. I do not like having NULL values in my tables.</p>
  
  <p>When I am dealing with a string field I can populate them with 'UNKNOWN' rather than NULL. I would like to do something similar with datetime columns. What is a good strategy, other than nulls, for dealing with SQL Server datetime columns with an unknown value?</p>