On what dates of July. 2004 did Monday fall?

Let us find the day on 1^st July, 2004.
2000 years have 0 odd day. 3 ordinary years have 3 odd days.
Jan.   Feb.   March   April   May   June   July
31 + 29 + 31 + 30 + 31 + 30 + 1
= 183 days
= (26 weeks + 1 day)
Total number of odd days = (0 + 3 + 1) odd days = 4 odd days.
∴ 1^st July 2004 was 'Thursday'
Thus, 1^st Monday in July 2004 as on 5^th July. Hence, during July 2004, Monday fell on 5th, 12th, 19th and 26th.