Calculation:
To determine the day of the week on July 24, 2011, we need to use the concept of "Zeller's Congruence." This formula allows us to calculate the day of the week for any given date.

Zeller's Congruence:
Zeller's Congruence is an algorithm devised by Christian Zeller to calculate the day of the week for any date in the Gregorian calendar. The formula is as follows:

h = (q + ((13 * (m + 1)) / 5) + K + (K / 4) + (J / 4) + (5 * J)) % 7

Where:
- h is the day of the week (0 = Saturday, 1 = Sunday, 2 = Monday, ..., 6 = Friday)
- q is the day of the month
- m is the month (3 = March, 4 = April, ..., 12 = December, January and February are counted as months 13 and 14 of the previous year)
- K is the year of the century (year % 100)
- J is the zero-based century (actually ⌊ year/100 ⌋) for the English calendar.

Calculation for July 24, 2011:
Using Zeller's Congruence, we can calculate the day of the week for July 24, 2011:

q = 24
m = 6 (July is counted as the 6th month)
K = 11 (2011 % 100 = 11)
J = 20 (⌊ 2011/100 ⌋ = 20)

Substituting these values into the formula:

h = (24 + ((13 * (6 + 1)) / 5) + 11 + (11 / 4) + (20 / 4) + (5 * 20)) % 7

Simplifying the equation:

h = (24 + (91 / 5) + 11 + 2.75 + 5 + 100) % 7
h = (24 + 18.2 + 11 + 2.75 + 5 + 100) % 7
h = (160.95) % 7
h ≈ 1

Therefore, the value of h is approximately 1. According to Zeller's Congruence, a value of 1 represents Sunday.

Conclusion:
Hence, July 24, 2011, was a Sunday.