You should know that there are:
7 days in a week
14 days in a fortnight
52 weeks in a year
365 days in a year
366 days in a leap year
Also, you should know the number of days in each month:
January | 31 |
February | 28 or 29 |
March | 31 |
April | 30 |
May | 31 |
June | 30 |
July | 31 |
August | 31 |
September | 30 |
October | 31 |
November | 30 |
December | 31 |
You could learn this poem:
30 Days has September,
April, June and November.
All the rest have 31,
except February which has 28,
until a Leap Year gives it 29.