In English, we do not always insert "on" when speaking of doing things on certain days. It is also legitimate to say "The doctor doesn't work Saturday."
Honestly, it sounds a bit strange to me. Maybe it's a regional thing. It's more acceptable to me to say "The doctor doesn't work Saturdays."
Having thought about it some more, I suppose that it's okay. For example, "I'm leaving Friday and returning Monday." I personally don't use it much, because I feel it's not quite correct. I'm from Sydney.
I'm OK with "Doctor doesn't work today," but "doesn't work on Saturday" sounds odd--as does "doesn't work September 6th." 55 years in California...
This wording would imply that the doctor isn't working this coming Saturday.
Since English has very little gender, I tried to give, "The lady doctor does not work on Saturday," but they marked it wrong. I wish they would accept an answer like that. It would make the full meaning of the Hebrew clear in the English.
On the other hand, you would not refer to a pediatrician as a child doctor (do you remember Doogie Howser?). But you could say "children's doctor." In the same folksy way, you could refer to a gerontologist as an "old folks' doctor" -- you wouldn't say an "old person doctor." I've heard women say, "For a gynecologist, I prefer a lady doctor to a male doctor." Likewise many men say, "For a urology or a prostate exam, I prefer a male doctor to a lady doctor (or a woman doctor, or a female doctor.) I think you'll hear it any of those ways. But I don't think I've ever heard someone say they want a "man doctor" meaning either a doctor for male health issues or a male doctor.
Oh I see, you need a plural for those the doctor treats. רוֹפֵא נָשִׁים is also a women's doctor. It might be a problem of my native German, were we have the same form for Kindersoldat (child soldier, a child who is a soldier) and Kinderarzt (pediatrician, a doctor who treats children).
I believe it accepts Shabbos, Shabbat, Saturday, Saturdays and Shabatot.