Prepositions of time

1. AT

1.1. hours

1.1.1. at 7 o'clock

1.1.2. at five o'clock

1.2. moments

1.2.1. at the moment

1.2.2. at the same time

1.3. other

1.3.1. at weekends

2. (-) no preposition

2.1. last

2.1.1. last Saturday

2.2. next

2.2.1. next week

2.3. this

2.3.1. this month

2.4. every

2.4.1. every year

3. IN

3.1. months

3.1.1. in January

3.2. seasons

3.2.1. in summer

3.3. years

3.3.1. in 2019

3.4. centuries

3.4.1. in the 21st century

3.5. weeks

3.5.1. in 4 weeks

4. ON

4.1. days of the week

4.1.1. on Monday

4.1.2. on Saturday morning

4.2. specific days

4.2.1. on Christmas Day

4.3. dates

4.3.1. on 24 June

4.3.2. on 12 December 2018