Being a bit familiar with celestial mechanics, I know that the Hohmann transfer orbit is the quickest way to transfer between two circular orbits of different radii around a central body in the same plane. JPL's Let's Go to Mars! Calculating Launch Windows explains the geometry and offers a very intuitive guide how to calculate the travel time to Mars, and this can easily be repeated for Venus.
Just for fun, I would like to mark all launch windows for a travel to Venus on a calendar, similar to the list compiled by Don P. Mitchell
1991, Jun 5 Unused Type I window 1993, Jan 5 Unused Type I window 1994, Aug 9 Unused Type I window 1996, Mar 20 Unused Type I window 1997, Oct 15 Cassini flyby
Question: I have a probably minor (astronomical) issue: I am struggling how to convert heliocentric longitudes into real dates? I guess I am missing the English terms here. I would appreciate a small reminder how to proceed.