pavrelmasti lujvo

x1 is December/the twelfth month of year x2 in calendar x3.

Duration. For date, use masngai. Cf. pavmasti, nanca.

In notes:

celma'i
x1 is December of year x2 in calendar x3.
pavmasti
x1 is January/the first month of year x2 in calendar x3.