Around 1640s, at what time did people eat Christmas dinner?
It is quite common knowledge the in times prior to modern conveniences such as electricity and natural gas for cooking the main meal would be anytime around noon to mid-afternoon.
Seeing that your question deals specificity with Christmas, it would probably be more around 12:00 PM or even a little earlier, depending on when the Church Faithful got home from the church services.
Please bare in mind that cities such as Paris or one’s further north start getting dark around 4:30 PM.
This practice of eating towards the midday is is done traditionally in some areas in Europe, notably in Benedictine Monasteries.
Most people ate two meals a day, dinner at midday, and supper, in the evening. Breakfast, as a separate meal, was a later concept. Those who worked in the fields either took food with them or someone brought it out to them when it was ready. The word lunch meant snack—something that could be eaten while walking or working—for quick energy. Fresh or dried fruit, perhaps with a piece of cheese, was a common lunch. - How Dining in the Middle Ages Differs From Now
Supper in Olden Days meant something generally different than in modern days: supper meant something more along the line of a very little meal or even a snack with some soup and served in the evening.
Exception to the rule are historically known, but generally amongst the very wealthy who could afford to light up ballrooms with candlelight.
Supper was originally a secondary lighter evening meal. The main meal of the day, called dinner, used to be served closer to what is known as lunchtime, around the middle of the day, but crept later over the centuries, mostly over the course of the 19th century. When dinner was still at the early time, eating a lighter supper in the evening was very common; it was not always the last meal of the day, as there might be a tea later. Reflecting the typical custom of 17th century elites, Louis XIV dined at noon, with a supper at 10 PM. Even when dinner was in the early evening, supper was served at, or on return from, a ball, and might be after other evening excursions. At an English ball in 1791, supper was served to 140 guests at 1:00 AM. They would all have had dinner at home many hours earlier, before coming out. Other, grander, balls served supper even later, up to 3:30 AM, at a London ball given in 1811 by the Duchess of Bedford.
Etymology
The term is derived from the French souper, which is used for this meal in Canadian French, Swiss French, and in Belgian French. It is related to soup. It is also related to the Scandinavian words for soup, soppa or suppe and the German word for soup, Suppe. The Oxford English Dictionary, however, suggests that the root, sup, remains obscure in origin.
Charles Dickens’ A Christmas Carol known the world over is surprisingly accurate in many historical facts around the subject matter of food, meals and drinks. This novel although published in 1843 holds to the basic urban living of the 17th century: no central heating or electric lightbulbs!
Alcohol flows freely in the writing of Charles Dickens. Though drinking was largely frowned upon in Victorian society, Dickens enjoyed drinking in moderation, and felt that nobody should begrudge the citizens of England this simple, age-old pleasure. Dickens was known to have a fondness for sweet alcoholic punches, which were quite popular at the time. One such drink, a mulled wine punch known as a Smoking Bishop, is mentioned in his timeless holiday classic, A Christmas Carol.
“A merry Christmas, Bob!” said Scrooge, with an earnestness that could not be mistaken, as he clapped him on the back. “A merrier Christmas, Bob, my good fellow, than I have given you, for many a year! I’ll raise your salary, and endeavour to assist your struggling family, and we will discuss your affairs this very afternoon, over a Christmas bowl of smoking bishop, Bob!”
Among the ‘Oxford night-caps’ bishop appears to be one of the oldest winter beverages on record, and to this very day is preferred to every other, not only by the youthful votary of Bacchus, at his evening revelry, but also by the grave Don by way of a nightcap. It is not improbable that this celebrated drink, equally known to our continental neighbours under the somewhat similar name of bischof, derived its name from the circumstance of ancient dignitaries of the church, when they honoured the university with a visit, being regaled with spiced wine. -Drinking with Charles Dickens – the smoking bishop