We write 8.1.1974 or 8th January, 1974 and we say the eighth of January, nineteen seventy-four or January the eighth, nineteen seventy-four
at
- clock time (six o’clock, 13:15);
- noon / night / midnight;
- breakfast / lunch / dinner time;
- holiday periods (Christmas; the weekend);
- the moment
on
- day of the week (Saturday);
- particular days (Christmas Day, that day);
- dates (January 18th);
- Monday morning / night;
- a summer’s day
in
- parts of the day (not night) (the morning / afternoon / evening);
- months (December);
- seasons (summer);
- years (1985);
- decades (the 1920s);
- centuries (18th century);
- Christmas holiday(s);
- two weeks’ time
without preposition
- today
- yesterday / the day before yesterday
- tomorrow / the day after tomorrow
- last night / last week
- next month
- yesterday evening
- tomorrow morning
- this evening
- tonight
- every day