The time difference between two places located at 30 degrees of longitude is 2 hours. This can be explained by considering the concept of time zones and the rotation of the Earth.

1. Introduction:
- The Earth is divided into 360 degrees of longitude, with each degree representing a distance of approximately 111 kilometers at the equator.
- As the Earth rotates on its axis, it is divided into 24 time zones, each covering 15 degrees of longitude.
- The time at any location is determined by its position within these time zones.

2. Understanding Time Zones:
- Time zones are based on the concept of dividing the Earth's surface into 24 equal parts, with each time zone representing one hour of time difference from Greenwich Mean Time (GMT) or Coordinated Universal Time (UTC).
- The Prime Meridian, located at 0 degrees longitude, is used as the reference point for determining time zones.
- Each time zone is approximately 15 degrees of longitude wide, extending 7.5 degrees to the east and west of the meridian.

3. Calculation of Time Difference:
- In this case, the two places are located at 30 degrees of longitude apart.
- As each time zone covers 15 degrees of longitude, the two places are in different time zones.
- Since each time zone represents one hour of time difference, the time difference between the two places is 2 hours (30 degrees / 15 degrees per time zone = 2 time zones).

4. Example:
- For example, if Place A is at 30 degrees East and Place B is at 60 degrees East, the time difference between them would be 4 hours (60 degrees - 30 degrees = 30 degrees / 15 degrees per time zone = 2 time zones = 2 hours).

5. Conclusion:
- In conclusion, the time difference between two places located at 30 degrees of longitude is 2 hours. This is because each time zone represents one hour of time difference, and the two places are in different time zones separated by 30 degrees of longitude.