so there are 378 or 379 days in the Netherworld year... interesting...
Fun fact: the Jacobin Club's French Republican Calendar has a "13th month" lasting 5 or 6 days, each day celebrating a certain aspect of life:
Virtue, Talent, Labor, Convictions, Honors; and The Revolution (only on leap years)
However it wasn't considered the 13th month when it was used during the French Revolution; just complementary days