The few monasteries I have stayed at have always eaten at the same clock time regardless of winter or summer time. 11am or 11.30am on the clock. I seem to remember it is for the convenience of the laypeople, so they don't get confused about what time they should come to give dana.
But one time I remember going out to do some shopping for the monastery (I was a long term lay guest), and I came back at 12.37pm... and to my horror I realised had missed lunch and I'd have to fast until the next day! Horror!
But then the Ajahn came in and said, "Check the solar noon, it's mid winter, so it may be later today."
I checked the newspaper for the solar noon, and I had three minutes! I quickly wolfed down some bread and half a cold pie and that was enough. Relief! You may have guessed I don't like fasting.
saturated with joy,
you will put an end to suffering and stress.