I am curious what town or city would be your choice as a day trip from Amsterdam.
It depends what time of year.
if April, Keukenhof.
Otherwise, Haarlem.
Depends on your interests. For churches, museums and history, i really liked Delft. For outdoors, in spring, I'd visit Lisse and the Keukenhof, or maybe the windmills and living museum village at Zaanse Schans
Also Leiden, Delft, Den Hague.
The RS guidebook has some suggested daytrips. Also see the book "Daytrips Holland, Belgium & Luxembourg" by Earl Steinbicker
Haarlem but not on Mondays or holidays.
In April of 2024, I based myself in Amsterdam (near Sloterdijk Station, great location) for my second trip to the area. I went to Keukenhof, Leiden, Haarlem and Zaanse Schans. I don't regret going to any of them. For day trips, I went to Leiden for half a day and just walked around and soaked up the atmosphere. If I go back to the area again, I would spend more time in Leiden. The second half of the same day, I went to the Keukenhof Gardens. Keukenhof was amazing and kind of a bucket list destination for me. They day I went, the weather was glorious and the flowers amazing. Haarlem was nice and I was able to go to the Corrie Ten Boom Museum (need to prebook weeks ahead) and St. Bavo's Church. My last day in the area was spent in Zaanse Schans. Yes, it is touristy but I really enjoyed it none the less. It was a great way to end my week long solo trip.
Definitely Keukenhof if it’s open. Haarlem, Hoorn & Leiden were all awesome. Not a full day but I also enjoyed strolling around Edam and Broek in Waterland…on my visit, I travelled on to Volendam and Marken that afternoon & could have skipped that part. Felt the same about Alkmaar- just too crowded for me on cheese market day. Haven’t been, but Utrecht is top of my list next time I find myself in the Netherlands.