day trip from Paris to Amsterdam

I would do the former, with at least one night in Amsterdam. Open jaws into Amsterdam, out of Paris shouldn't cost more than in and out of Paris, and you'd save the time and expense of a trip between Paris and Amsterdam. Better yet, if you are spending one day in Amsterdam, do it at the end of your trip when you are not jetlagged. As for a day trip, if you left Paris at 8 AM on the fastest (most expensive train and returned at 8 PM, the fastest round trip is 6½ hrs. You'd have, maybe, 5½ hrs in Amsterdam. So little time in Amsterdam would hardly be worth the time getting there and back.

Huh? It's three hundred miles, more or less, by road. I have no idea how trains work, but assuming a straight track and sixty mph with no changes, it's got to be close to four hours each way, maybe three and a half. Amsterdam Centraal is close enough to everything that walking time is inconsequential, but Paris Nord is a bit inconvenient from where most people stay, so figure another half hour from your hotel to the station, finding the right track, etc. Go ahead and call the whole deal four hours, just for grins. There's probably a combination of slow and fast trains, but, odds are, leaving twixt seven and eight, you won't get there until noon. I THINK that the last train back leaves around five. To hump back to Central, you need to stop goofing around by four-thirty. I think you're looking at fourteeen hours of grind, only four of which will be spent looking around - - and you've got to fit a meal in there somewhere. If Tim wanders by, he can refine my horrible train knowledge, but the logic is in there somewhere. EDIT: or just listen to Lee who was typing at the same time.

Two years ago I flew into Amsterdam (arriving around 7:00 a.m.) and spent only one night before taking the train out the next day for Bruges. I flew home from Paris. It was no more expensive to fly into Amsterdam that it would have been to fly round trip to Paris. Doing it this way you only have to buy a one-way train ticket to Paris. How much time with you have in Paris? FYI if you arrive early and can't check into your hotel, the train station has lockers that are good for 24 hours. We stored our bags there and only took a small tote bag to our hotel with overnight things. We were able to drop our overnight bags there early, and then checked in much later in the day.

I'd fly into Amsterdam - the airport is so much more arrival friendly than CDG in Paris because it's a whole lot easier, faster and cheaper to get into town from there. The train at the airport drops you at the central station in the city and it's easy to get places from there. Also, if you're going in April, you ought to visit fabulous Keukenhof for the spring flowers (google it). Also very easy, cheap to get to and it doesn't take long. A half day is enough for getting there and walking through. Do it early in the morning, it gets really crowded with tour buses later. You'll want to do a canal boat trip, too, among the other fabulous sites and sights. You could do this on your arrival day. Also easy (across from the central station) and not expensive. I'd spend two nights and then go on to Paris. Reserve your room well in advance, in both places.

The fastest train from Paris to Amsterdam is Thalys, direct from Paris Nord to Amsterdam via Brussels, Antwerp, Rotterdam, and Schiphol in 3h18m. Trains leave Paris at 7:25, 8:25, and 10:25, at least for the day I checked. The last of those 3+hr trains leaves Amsterdam at 7:16 PM. So, if you left Paris on the 7:25 train and came back on the 19:16 train, that would be 15 hrs not including getting to/from Paris Nord, and you would have 8½ hrs in Amsterdam.

We have 7 full days not counting travel days from the states. It sounds like flying into Amsterdam and taking the train to Paris is the way to go.
Thanks

Have you ever been to Europe? The day you arrive will be very difficult due to jetlag and travel fatique. You'll have trouble staying awake. A full day of sightseeing in Amsterdam, followed by a late train to Paris and having to navigate Paris at the end of a long, tiring day will be tough. That's why I recommended either spending the night in Amsterdam and training to Paris the next day, or hitting Paris first and going last to Amsterdam to fly home (although that might require an overnight stay in Amsterdam, as well).

LOL, yes Lee, I have been to Europe a number of times. I am on the phone right now booking a couple of night in Amsterdam.