4 days in amsterdam or 3 + 1 day trip?

What is your full itinerary? I saw you posted on another board about Germany...might be helpful to hear how many days total you have, where you plan to fly in and out of, what your interests are, etc. Amsterdam is a great city that can definitely fill 4 days, esp. given a jetlagged arrival day, but will you go back to Europe in the future or is this a one-time deal? Bruges and Ghent (Belgium) are a good day trip nearby.

hi, current itinerary is 4 days amsterdam, 4.5-5.5 days berlin (depending on if a day is moved to dresden, 3 days prague, 5 or so days austria (salzburg/vienna). I hope to come back at some point but probably not to any of these places any time soon

An easy day trip from Amsterdam would be Haarlem, about 20 minutes by train, with its Great Church and market square, the Franz Hals Museum, and other attractions. Could be a half day.

I understand Leiden and the Hague are also good day trip destinations but I haven't been there. Tomfromleiden may appear soon on this thread! ;-)

I wouldn't dare to disappoint Dick...
Do yourself a favour and get out of the busy, crowded and over-touristy city for one day. You've got a wide choice and everything is perfectly connected by train.
The Hague is the place if you're a devotee of the Dutch Golden Age with the Mauritshuis museum, or of Mondria[a]n, for whom you have the Gemeentemuseum. The immediate area around the Mauritshuis is agreeable, but otherwise I can tell you from personal experience it is not a overly nice city.
Haarlem has indeed its wonderful Markt square with the church, the city hall and assorted historical buildings. If you're into art, the Frans Hals Museum is a must and the Teylers Museum is a late-18th-century gem of a science museum.
Leiden has the largest historical centre after Amsterdam, is the city where Rembrandt learned his trade and a wonderful place for wandering (and wondering) around, especially around the two large churches which you can spot on any reasonably detailed map. Go there on a Saturday, which is market day along the canal behind the city hall.
For a different experience you could have a nice day trip to Hoorn and Enkhuizen, north of Amsterdam, both historical harbour cities and founders of the Dutch East Indies Company from the days they were still on an open sea inlet. Enkhuizen is almost a village, Hoorn is more grand and has the interesting Westfries Museum in an impressive historical building. Enkhuizen is 1 hour by a direct half-hourly train with Hoorn halfway on the same line (you are allowed to break your journey on the same ticket).
Use www.ns.nl as your train planner.

thanks so much for the replies especially the detailed info from tonfromleiden, really appreciate them!