IN
segundos		in twenty seconds, in thirty seconds' time
minutos		in a minute, in ten minutes, in ten minutes' time
horas		in an hour, in ten hours, in ten hours' time
dias		in two days, in thirty days' time
semanas		in a week, in two weeks, in two weeks' time
meses		in a month, in two months, in a month's time, in January, in July, in May 2000, in June 2001
anos		in 1959, in 1980, in 1999, in 2001
décadas		in the 1960s, in the 1970s, in the 1990s
séculos		in the 19th century, in the 21st century
partes do dia		in the morning, in the afternoon, in the evening, in the night (1)
estações		in (the) spring, in (the) summer, in (the) autumn, in (the) winter
festivais		in Easter week, in Ramadam
períodos		in that time, in that year, in that period

 
 
 

		ON
dias da semana		on Sunday, on Monday, on Tuesday, on Sundays, on Mondays, on Tuesdays
partes do dia		on Sunday morning, on Monday afternoon, on Wednesday evening
datas		on 21st January, on June 10th, on 2nd May 1990, on 30th June 2000
aniversários		on my birthday, on our wedding day
festivais		on Christmas Day, on New Year's Day, on Good Friday, on Easter Sunday
acontecimentos		on that day, on that afternoon, on that evening

 
 
 

		AT
festivais		at Christmas, at Christmas-time, at Easter
horas exactas		at seven o'clock, at twelve thirty, at 3.30 p.m., at midday, at midnight, at noon
idades		at sixteen, at the age of 18
outras		at dawn, at this time, at that time, at tea time, at lunch time, at dinner time, at the weekend, at night (2)

 
 
 

		NO PREPOSITION
all		all morning, all day, all week, all month, all year
every		every morning, every day, every week
last		last night, last Friday, last week, last month
next		next Friday, next week, next month, next year
tomorrow		tomorrow, tomorrow afternoon
yesterday		yesterday, yesterday morning
outras		the day before yesterday, the day after tomorrow

 
 

(1) in the night refere-se a uma noite específica

(2) at night refere-se a uma noite como uma outra qualquer