What characteristics did the early Roman Calendar in the Islamic calendar share?

Lunar cycle and days of month.

Explanation:

The use of lunar cycle is the similarity which is present in both early Roman Calendar and Islamic calendar. In early roman Calendar as well as the Islamic Calendar, they use the shapes of moon for the starting and ending of the month. The first month of both Calendars start with the sign of new crescent moon. In both calendars, each month consist of 29 to 30 days because moon completes its cycle in 29 to 30 days.

yes they have. but is this a true false question? if it is, the answer is true.