Catharine wrote:

I somehow managed to split my calendar into tw; one a subfile.

Calendars are not files, they're folders.

I believe it happened with my palm pilot. But, I need to put my
calendars back together into just one.

Open one, select all of its contents (view it in a table view and press
CTRL-A), right-click and drag the selection to the default calendar, then
choose Copy or Move as is appropriate to you.
--
Brian Tillman