Peter?

When was the last time you laid out a trip; point to point in Hours?
That is the hook!

A DR route point to point is laid out in Distance. (Miles not time) Each
leg to your Swertheart would be four legs, point to point in miles, with
calculated Drift/mile vectored in. Compass Dev & Var considered to set
up your course heading. When you had that all done, then and only then
would you estimate the lapsed time.
The old saying Pete, "Sailors schedule only departure times, after that
they only have control of direction."

Hope this clears up the problem.

Ole Thom