Adjective modifier

• few: These first few days will also be used to analyze the different ideas for your final project.

Converse of object

• spend: This is why they spent the first day after the election appealing to Fatah to join them in government.

Possessives

• trading: It is not unknown for stocks to climb 500 % on the first day's trading.

Preposition: in

• school: Nobody wants to play with Lucy on her first day in school.

• uniform: How well I recall my first day in uniform.

Preposition: of

• spring: Every day will be the first day of spring for you now.