How to find any day using given date and year?

Question

I am posting after a long time here. I am having trouble finding solution to this types of problem. Please help me out on this case:

If the 1st December, 1994, was Thursday, then what was the day on the same date in year 1995?

All I know it's related to Doomsday rule from Dr. John Conwa, but I need a clear explanation on how the calculation actually works.

Please help me out here.

Answer 1

$1994$ and $1995$ aren't leap years, thus both of them have $365$ days.

The same day repeats exactly after $7$ days (that's what week is) so basically after $700$ days ($700=7\cdot 100$) it's still a Thursday.

Now we are $365$ days away and $364$ is the last multiple of $7$ up to $365$ thus after $364$ days it's still Thursday and obviously after a day it would be Friday.

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If it were to be let's say $20$ February $2000$ a Monday (in a leap year), by the same logic $20$ February $2001$ would be Wednesday.

Answer 2

Hint:

Taking Dec 1, 1994 (Thursday) as Day-1. What is the date on Day-365 and hence the date on Day-366? What is the day on Day-8? On Day-15? On Day-22?

Can you take it from here?