先月 Sengetsu
If you're referring to the month, it is "gogatsu."
去年 /kyo nen/ means 'last year' in Japanese.
the month be fore last
You may say 'senshuu no nichiyoubi.'
The Japanese word for "monthly" is 毎月 (maigetsu), which literally means "every month".
先週 senshū
saigo no enjerusureija
le mois dernier
Rokugatsu (六月). It literally translates to "sixth month" in Japanese, I believe, but that's what they call June. You could also say it as "juun", but that's just "Engrish"; a Japanese pronunciation of the English word.
"No, mes pasado" means "No, last month".
Le mois dernier
Fue el mes pasado.