tenia un buen fin de semana
Yes, the possessive form of the noun week is the correct form for 'the end of the week' (the week's end).
La semana.
esta semana
La semana.
This is how you would say it. What do you do on week ends?
Cada semana.
le week-end - la fin de semaine
Translation: Una semana
hace una semana
Ayez un week-end agréable or Bon week-end
El fin.