Use forms of бІть for the past and future of short adjectives.
Short adjectives have a verbal meaning ('am/is/are'); with forms of бІть they mean future and past.
Онђ больнђ. She's sick. Мнљ нужнІ карандашќ. I need pencils.
Онђ былђ больнђ. She was sick. Мнљ нужнІ бІли карандашќ. I needed pencils.
МІ бІли больнІ. We were sick. Мнљ нужнІ бџдут карандашќ. I'll need pencils.
Ї увљрен(а) в ітом. I'm sure of that. Мнљ нужнђ былђ рџчка. I needed a pen.
Ї бІл(ђ) увљрен(а) в ітом. I was sure of that. Ћн мнљ бџдет нџжен. I'll need him.
Онђ былђ увљрена в ітом. She was sure of that. Ї емџ бџду нџжен (нужнђ). He'll need me.