This trick must be used when we need to calculate previous date from the given date.
On 10 September 1991 was Tuesday. so What was The day on 13 March 1991.
First of all we must Know:
0th odd day=Sunday
1th odd day=Monday
2th odd day=Tuesday
3th odd day=Wednesday
4th odd day=Thursday
5th odd day=Friday
6th odd day=Saturday
STEP 1 :
First of all we calculate the total number of days between the date 13 March 1991 to 10 September 1991
|Number of Days in1991|
|Total No. of Days||181|
STEP 2 :
Now we calculate the odd day number and for that we have to divide the total number of days with 7(1week=7days) and reminder will be our odd day number.
181 / 7 = 6 odd days (6 is Reminder)
STEP 3 :
As we know given day is Tuesday which is 2th odd day
Let the odd Number associated with the day on 13 March 1991 is 'X'
Tuesday on 10 September 1991 = 2 odd day
so 'X + 6 = 2'
Now we have to put the value of 'X' as after dividing 'X + 6' with '7' reminder will be '2'
so 'X = 3' and day is 'Wednesday'