The time period for 15 of longitudes is 60 minutes.

To understand this, we need to know that a full rotation of the Earth takes 24 hours to complete. During this time, the Earth rotates 360 degrees, which means that each hour corresponds to a rotation of 15 degrees.

Since there are 24 time zones around the world, each time zone covers 15 degrees of longitude. Therefore, each time zone represents a time difference of 1 hour from the adjacent time zone.

In other words, when it is noon in a location at a particular longitude, it will be 1 PM in the location 15 degrees to the east, and it will be 11 AM in the location 15 degrees to the west.

So, when we talk about a time period of 15 of longitudes, it covers a span of 1 hour, which is equivalent to 60 minutes.

Therefore, the correct answer is option 4, 60 minutes.