who introduced the aforesaid calender?
Pope Gregory XIII.
Gregorian calendar
The Gregorian calendar is the calendar used in most of the world. It is named after Pope Gregory XIII, who introduced it in October 1582. 
which ports had trade links with south asian parts Arsinoe, Berenice and Myos Hormos. between whom did the trade take place? The Roman Empire and the Indian Subcontinent. when did it begin? Around the beginning of the Common Era (CE) following the reign of Augustus and his conquest of Egypt in 30 BCE. what more can you about this era? Common Era (CE) is one of the year notations used for the Gregorian calendar, the world's most widely used calendar era.
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Gregorian calendar [SEP] Introduction
The Gregorian calendar is the calendar used in most of the world. It is named after Pope Gregory XIII, who introduced it in October 1582. The calendar spaces leap years to make its average year 365.2425 days long, approximating the 365.2422-day tropical year that is determined by the Earth's revolution around the Sun. The rule for leap years is: Every year that is exactly divisible by four is a leap year, except for years that are exactly divisible by 100, but these centurial years are leap years if they are exactly divisible by 400. For example, the years 1700, 1800, and 1900 are not leap years, but the years 1600 and 2000 are.