Hi Roberto,
Thanks for the question. If it is a specific year, use the past tense.
If it is “any” year – for example, see our task 1 question about precipitation – then use the present tense. In other words, if you don’t know the specifics of the time period, use the present tense. Also, if there is a projection into the future (see our population question), then you should use past and future.
