Unless means the same as if...not. Like if, it is followed by a present tense, a past tense or a past perfect (never by 'would'). It is used instead of it + not in conditional sentences of all types:
Type 1 (Unless + present)
a. You´ll be sick unless you stop eating. ( = You will be sick if you don´t stop eating)
b. I won´t pay unless you provide the goods immediately. ( = If you don´t provide them I won´t pay)
c. You´ll never understand English unless you study this grammar carefully. ( = You´ll never understand if you don´t study... )
Type 2 (Unless + past)
a. Unless he was very ill, he would be at work.
b. I wouldn´t eat that food unless I was really hungry.
c. She would be here by now unless she was stuck in the traffic.
Type 3 (Unless + past perfect)
a. The elephant wouldn´t have seen the mouse unless she´d had perfect eyesight.
b. I wouldn´t have phoned him unless you´d suggested it.
c. They would have shot her unless she´d given them the money.
Por hoje é só. Amanhã tem mais. See you.