Children’s book I read in the 60’s with time travel

[Laura]

I’m looking for a book I read in the late 60’s where a girl is visiting her grandfather and ends up time travelling to the past. I remember the house was described as odd with stairways that went nowhere. The girl opens a door and steps through into a garden that turns out to be in the past. She meets some other children who think she is an apprentice - they think her short dress is an apprentice’s livery. That’s really all I remember but it is a vivid image and I would love a chance to reread this book if anyone can help with the title.
Thanks!