The time difference between the two cities, city A (30'N 60'E) and city B (30'N 80'E) would be

The time difference between two locations is determined by their difference in longitude. The Earth rotates 360° in 24 hours, which equates to 15° per hour or 1° every 4 minutes [c1]. City A is located at 60°E and City B is at 80°E. Since both cities are in the same hemisphere (East), the longitudinal difference is calculated by subtracting the smaller value from the larger: 80° - 60° = 20° [t1]. To find the time difference, this degree difference is multiplied by the rate of 4 minutes per degree: 20° × 4 minutes/degree = 80 minutes [c1][t2]. Therefore, the local time in City B is 80 minutes ahead of City A because it is further east [c1]. The latitude (30°N) does not affect the calculation of solar time differences, as time is strictly a function of longitude [c1][c2].

Sources

1. [1] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 2: The Earth's Crust > Longitude and Time > p. 11
2. [2] Exploring Society:India and Beyond. Social Science-Class VI . NCERT(Revised ed 2025) > Chapter 1: Locating Places on the Earth > Before we move on ... > p. 24