When we were there, we went on a Thursday. Not sure if that was a summer thing, but could check to see as it will double your opportunities to go.

All I know is that the Saturday antique market is an all day affair. As I recall it opens at 10 and closes in the late afternoon. If it's raining, I think things close up earlier. It you are in the area on a Thursday, it's worth going to Gouda, not far away in the early morning (9 o'clock on, I think until 11or a bit later). They set up in the town square with huge wheels of Gouda cheese and there is a bidding war. They do something like whistle to bid.

I think it is only Saturday. Even if the market isn't on, there is enough to to see in Delft anyway. Have a great day.

9 am - 5 pm. If you're flexible lunchtime is the best & tastiest;)

It starts in the morning, at 9am, and ends in the afternoon around 5pm. The best moment to go, from my point of view is lunch time!

Delft is approximately 1 hour by train from Amsterdam. The flea market is not close to the station. You would need a bus or taxi to get there. Best to stay overnight to visit this lovely Dutch city.

Yes, it should be open in March. You should really enjoy it. There is also a Saturday Market in Linden if you are interested.