The word 'day' can mean two things: it can mean the hours when the sunshine's, or it can mean a 'calendar day'.

In the second case, day and night are taken as one. The calendar day is always twenty-four hours long; that is how long it takes for the Earth to turn once on the axis. In the first case, the meaning of the word 'day' is quite different. In face, no two days have an equal amount of sunlight.

On 21 June, at the beginning of the summer, there are sixteen hours of light between sunrise and sunset, but only eight hours of daylight on 21 December. At the beginning of spring and autumn, the number of hours of daylight is midway between sixteen and eight, so the day and night are always the same length. Remember, whilst it's summer in the northern hemisphere, it's winter in the southern hemisphere, and vice versa.

In the winter, we get less sun, less heat, less light. It gets dark early, especially when the sky is cloudy or it rains.

To sum up day and night are the same length in summer and winter. It merely gets darker earlier in winter.