Prepositions At a glance

English	Usage	Example
on	days of the week	on Monday
in	months / seasons time of day year after a certain period of time (when?)	in August / in winter in the morning in 2006 in an hour
at	for night for weekend a certain point of time (when?)	at night at the weekend at half past nine
since	from a certain point of time (past till now)	since 1980
for	over a certain period of time (past till now)	for 2 years
ago	a certain time in the past	2 years ago
before	earlier than a certain point of time	before 2004
to	telling the time	ten to six (5:50)
past	telling the time	ten past six (6:10)
to / till / until	marking the beginning and end of a period of time	from Monday to/till Friday
till / until	in the sense of how long something is going to last	He is on holiday until Friday.
by	in the sense of at the latest up to a certain time	I will be back by 6 o’clock. By 11 o'clock, I had read five pages.