I am working on upgrading our database from FM6 to FM7. The old database needs a lot of work to make it efficient, reliable, and attractive. I am working on a copy of the data, making the necessary improvements and enhancements in FM7. Meanwhile, however, the old database is still being used. I will need to identify and import to the new version the records changed or added between the time I created my working copy (already a couple of weeks ago) and the time the new version is ready. What is the best means of doing this? At present there is no field in the old database which reliably identifies the day on which a record is added or modified. Should I add such a field, and if so, how?

I am aware, of course, that I should have planned this more carefully at the outset, but it has been a bit of an ad hoc project, growing unexpectedly as we have come to realize the possibilities for improvement.

You should work on the FM7 version offline, then when it's ready, import all the live FM6 data. This import process will be easier if you only have to deal with it once. There will also be less confusion and less chance of missing something.