去年

去年 (qùnián) means 'last year' — the calendar year before the current one. The first character 去 normally means 'to go,' but here it carries an older sense of 'past / gone by,' the same sense as in 过去 (guòqù, 'the past'). 去年 functions as a time noun, so it goes BEFORE the verb in a sentence: 我去年去了北京 ('I went to Beijing last year'), never *我去了北京去年.

It can also stand at the very start of the sentence as a topic: 去年我很忙 ('Last year I was busy'). Because it already marks past time, you don't need 了 to make the sentence past — though 了 often appears with the verb to mark a completed action. The matching set is 前年 (qiánnián, 'the year before last'), 今年 (jīnnián, 'this year'), 明年 (míngnián, 'next year')