Complex sentence: In March 1229, on Shrove Tuesday, Paris's pre-Lenten carnival was coming to its conclusion, similar to the modern-day Mardi Gras, when one wore masks and generally let loose.
Split into simpler sentences: In March 1229, on Shrove Tuesday, Paris's pre-Lenten carnival was coming to its conclusion. This was similar to the modern-day Mardi Gras where one wore masks and generally let loose.