If 18th February 1997 fell on Tuesday then what was the day on 18th February 1999?

Thursday

In an ordinary year , Number of odd days = 1 day

In a leap year , Number of ordinary days = 2 day

Odd days in 1997 (Ordinary year) = 1

Odd days in 1998 (Ordinary year) = 1

So, total number of odd days = 1 + 1 = 2

Day on 18th February 1999 = Tuesday + 2 next days = Thursday