On,by,at,in?
Когда пишется On,когда by,когда in,a когда at?Хотелось бы увидеть цельную картину.

Question

On,by,at,in?
Когда пишется On,когда by,когда in,a когда at?Хотелось бы увидеть цельную картину.

Answer

The prepositions in, on, and at can be used to indicate time and place. Notice how they are used in the following situations:
Preposition 		Time 		Place

In

Year, Month, In 1999, In December

Country, State, City In Japan, In Utah, InTaipei

On

Day, Date On Saturday, On May 1

Street On Main Street, On 1st Ave.

At

Time At 8:00, At 7:30

Address At 815 East Main Street

In many languages, there is only one preposition for the above situations. In English there are three. Just remember that in usually indicates the "largest" time or place, and at usually indicates the "smallest" time or place. 
"by"  can  also  be a preposition meaning in proximity to , or near 
Example:  I was standing by the window

Answer

It is impossible to give a rule about these words. They are best learned in context. But the following pages can help:

http://www.englishclub.com/grammar/prepositions-at-in-on-place.htm

http://www.englishclub.com/grammar/prepositions-at-in-on-time.htm

Answer

You can only work this out by looking at actual examples.

Answer

You may look here about using "on, at and in" here:
http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/learnitv94.shtml

"By " is using when you must have done something up by the given time.
by 5 o'clock = к пяти часам (что-то должно быть сделано к этому времени)