How to memorise important Dates & Numbers

Best and simplest is to revise and recall again and again. But somewhere you may be confused. For this, you can use some tricks.

Phonetic System, Peg system, Alphabet System.

Pick a random word then find any connection and write the second word, then again find a connection and write next word, this way make a chain of linked words. Next day start with the same word and make a chain and compare with last words of yesterday and compare the whole chain, is both are same or different. Do this exercise for some days:
Rose, Red, Blood, Ambulance, Signal, Train, Tea, Sugar, Candy, Orange
Second level: now put a time limit on this exercise like 30 seconds for 20 words.

Pick a word and start making chain do this exercise for some days.
Third Level: 
For this, you can take help of your friend. Request him to give you some random words one by one and you should write the first idea come into your mind relating to that word it may be anything but be careful you have to write down only first idea hit into your mind.

What will it do? It will train your mind and in one direction. Right now we have random ideas generated in our mind. This will improve our recalling power. It will make easy to apply other methods also.

Convert a number into language: 
Convert numbers in your daily informally used words. Like in Hindi 7 "Saath" together, 12 "Bahar" outside 13 "tera" yours...
You can make your own, choose very easy and hit in your mind if one thing encounters with you. ...and convert into a line
In this way we are making a network one thing is linked with another. And this network makes it easier to remember things
for long term.
For example cube of 12 is 1728 in Hindi " Ek Saath Dono Edhar aajao Bharchalenge" can make ever better and interesting.
It takes time but if you make strong and logical then it will last for a long time long.