UTC
Sun crosses the celestial equator heading north — spring begins in the Northern Hemisphere. Ideal date for solar declination calibration.
二至点和二分点日期根据 JPL DE440 星历计算（与 NASA 使用的行星/月球星历相同）。流星雨峰值日期与 ZHR 值遵循国际流星组织（IMO）年度日历。行星事件数据来自 NASA Horizons 系统。
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