You can find anything at the time table of NS. It is in English. The frequency in the Netherlands is high, mostly every thirty minutes or even better.

Welcome to the NS Community!

There are no restrictions for domestic trains (your ticket will take you there) but for travel info I highly recommend https://www.rijdendetreinen.nl/en and their app.

In addition to Thom and Robert B; you can take the train at anytime, you are not restricted to any one time for the ticket. You are free to pick one as you go.

So , if I bougth tickets on NS app, then I can hop on any train I like on the day the tickets are bought for?

Exactly. Regular tickets have no restrictions.

Be sure you bought a regular ticket. Cheap tickets do have restrictions in general. It is mentioned on the e-ticket. It is mostly with limitations during peek-hours.

Thank you all! I hope everything will go smothly :))