Compare at, on and in: They arrived at 5 o'clock. They arrived on Friday. They arrived in October or in 1998. We use at for the time of day: at five o'clock at 11.45 at midnight at lunchtime at sunset We use on for days and dates: on Friday/Fridays on 16 May 2009 on Christmas day on my birthday We use in for longer periods, for example: months/years/seasons in October in 1998 in the 18th century in the past in (the) winter in the 1980s in the Middle Ages in (the) future We use at in these expressions: at night - I don't like working at night at the weekend/ at weekends - Will you be here at the weekend? at Christmas - Do you give each other presents at Christmas? at the moment / at present - The manager isn't here at the moment/ at present. at the same time - Kate and I arrived at the same time. We say: in the morning(s) - but on Friday morning(s) in the afternoon(s) - but on Sunday afternoon(s) in the evening(s) -...