la grand semaine

You can say C'est la grande semaine. It works perfectly as a standalone statement. You can also add it to a longer sentence. Je me prépare pour la grande semaine. It sounds natural and very clear. Use it to set expectations with your friends. People will immediately know you are busy. It is like a verbal 'Do Not Disturb' sign but with more flair.

Use it at work before a major product launch. Use it at home before a big move to a new house. It is perfect for stressful times like final exams. Use it when you feel slightly overwhelmed. It helps people empathize with your situation. "Ah, the big week!" they will say back to you. It is great for building rapport over shared stress.

Do not use it for a lazy vacation week. If you are sitting at the beach, skip it. Unless you are doing a lot of extreme surfing. Do not use it for a normal, boring week. It loses its power if you use it every Monday. Keep it for the truly intense times. Also, avoid it in very tragic situations. It is for 'busy' big, not 'sad' big.

The French value their temps libre or free time deeply. A grande semaine is a notable break from the usual work-life balance. It is often used in the worlds of fashion and politics. Think of 'Paris Fashion Week' or an election cycle. It implies a temporary peak in activity. It is a socially accepted reason to be débordé (overwhelmed). In France, admitting you are busy is a sign of importance.

You will often hear people say une grosse semaine. This is very common in offices. Une semaine chargée is another way to describe a packed schedule. La semaine sainte is a specific religious term for the week before Easter. But la grande semaine sounds more epic and cinematic. It feels like the title of a movie about your life.