去年 could come first in the sentence as well, but wasn't allowed.

去年 can be placed also at the beginning of the sentence, just before the subject. Please look at this explanation:

"Time words can appear in one of two positions in the sentence in Chinese: either at the beginning of the sentence (before the subject), or directly after the subject. The structures are:

Time + Subj. + Verb + Obj.

Subj. + Time + Verb + Obj."

Source: https://resources.allsetlearning.com/chinese/grammar/Time_words_and_word_order

Can someone add the other alternative, please?

what is the difference between 上年 and 去年 ?

no 了?

Reporting it since it still didn't accept "去年" at the front of the sentence...

I'm really irritated with the inconsistency between past and future tense particles, in Chinese.