时间系统转换： --其转换过程把通用时、GPS时间、和年积日分别转换为儒略日，然后以儒略日为中转，实现任意两个时间系统的相互转换
Time System Conversion: Converting Universal Time, GPS Time and Yearly Accumulated Days into Julian Days respectively, and then using Julian Days as Transit Time to realize the mutual conversion of any two time systems.