What Is The First Day Of Summer 2025 Kalender. The first day of winter is marked by the winter solstice, which occurs when the earth’s axis tilts farthest from the sun. Here’s what to know about the summer solstice in the northern hemisphere on thursday.

May 1 (mon.) last day to apply for undergraduate admissions for summer and fall semester 2025: Is the summer solstice the first day of summer?