on on a certain day
on a sudden(突然)
on a winter morning
on Christmas Day
on night shift
on one's birthday
on schedule(按時(shí))
on Sunday,on that date
on this occasion
on time
at at a time(在某時(shí))
at a wedding(婚禮)
at all times(一直)
at any moment,at any time
at Christmas
at dark(天黑時(shí))
at dawn(在黎明)
at daybreak
at dinner-time
at dusk(在黃昏)
at Easter
at first sight(一見到)
at first,at last
at midnight,at night
at nightfall,at noon
on a sudden(突然)
on a winter morning
on Christmas Day
on night shift
on one's birthday
on schedule(按時(shí))
on Sunday,on that date
on this occasion
on time
at at a time(在某時(shí))
at a wedding(婚禮)
at all times(一直)
at any moment,at any time
at Christmas
at dark(天黑時(shí))
at dawn(在黎明)
at daybreak
at dinner-time
at dusk(在黃昏)
at Easter
at first sight(一見到)
at first,at last
at midnight,at night
at nightfall,at noon