What explains the fact that different places on earth have seasons at same time of theyear?

The seasons are caused by the tilt of the Earth's axis as it orbits the Sun. As the Earth orbits the Sun, different parts of the planet are tilted towards or away from the Sun. This causes the amount of sunlight that reaches different parts of the Earth to vary, which in turn causes the seasons.

When the Northern Hemisphere is tilted towards the Sun, it receives more sunlight and experiences summer. At the same time, the Southern Hemisphere is tilted away from the Sun and experiences winter. Six months later, the Earth has moved around its orbit so that the Southern Hemisphere is tilted towards the Sun and experiences summer, while the Northern Hemisphere is tilted away from the Sun and experiences winter.

So, the fact that different places on Earth have seasons at the same time of year is due to the tilt of the Earth's axis as it orbits the Sun.