In FM6 how would you pass the contents on one field to another field in a different database (both are opened)? Do you "copy" the contents to the clipboard and then "paste" to the other field (from the other clipboard)?

You could, although it would be more highly recommended to use a relationship and use Set Field. Are your two files related? What determines into which record the copied data would be pasted?

Say a popup calendar. When the user clicks on a day the date field is filled in with the selected day. The calendar is another FM database.

Someone who is more familiar with popup calendars can probably answer your question, but it sounds as if Copy/Paste may be the best solution in this case.