As known,
Number of odd days upto 30 june 1974 =
(odd days for 1600 years +
odd days for 300 years (Number of odd days in 300 years = (5 x 3) 1 odd day.)+
odd days for 73 years )
= 0 + 1 + ((18 x 2) + (1 x 55) )
= 0 + 1 + 0=1 odd days

odd days of 30 days of june 1974=
Number of days according to the months are
January = 31 days
February = 28 days
March = 31 days
April = 30 days
May = 31 days
June = 30 days
Therefore, 31 + 28 + 31 + 30 + 31 + 30 = 181 = 25 weeks 6 days ≡ 6 odd day
total odd days=1+6=7
Therefore ,30th june 1974 was a sunday.