SERVILIA: To a modern audience, these lines can sound a little confusing; but Shakespeare’s audience would have picked up on their meaning because they were more attuned to the movement of the sun, moon, and stars than we are today.

RALPH: The men are arguing about where the sun will come up on the horizon, but to know this requires knowing the exact date. That’s because the sun only rises directly in the east during the equinoxes in fall and spring. 

SERVILIA: In the northern hemisphere’s winter, the sun rises farther south. And in the summer, it’s rises farther the north. For example, in London, the sun rises 40 degrees south of east in mid-winter, and 40 degrees north of east in mid-summer.

RALPH: At the beginning of this scene, Brutus makes a similar comment, noting that he could not tell the time by the position of the stars. 

SERVILIA: Due to the earth’s rotation, the stars appear to circle around the North Star every 24 hours. But as the earth moves around the sun, the portion of the celestial sky that is visible each night slowly changes. 

RALPH: For example, a constellation that rose this morning at 3:00am will rise an hour earlier in two weeks. So, telling the time from the position of the stars also requires accurately knowing the date.

SERVILIA: Like all early civilizations, Rome defined a month as one lunar cycle, and used a 12 month lunar calendar. Unfortunately, 12 lunar months only add up to 355 days, 10 short of the actual 365 days in a year. So these early lunar calendars drifted by 10 days each year.

RALPH: So if you didn’t adjust the calendar, a religious festival that normally celebrated the arrival of spring would fall in the middle of winter after a few years. To get the lunar calendar back in alignment with the solar year, extra months would have to be tacked onto the end of a year every once in a while. 

SERVILIA: This haphazard system of adjusting the Roman calendar resulted in a huge variability in when dates actually occurred. For example, the Ides of March, the 15th day of the third month of the year, might actually fall anywhere between late January and early May. Therefore, since the Romans didn’t know the true solar date, they couldn’t tell where the sun would rise, or what time it was at night.

RALPH: The official responsible for declaring when these extra months were to be added was the Pontifex Maximus. As it happens, Caesar had managed to get himself elected to this prestigious lifetime position early in his career. 

SERVILIA: While passing through Egypt during the civil war, Caesar learned that the Egyptian scientists had accurately measured the length of the solar year. On his return to Rome, he implemented the Julian calendar—taken from his name, Julius—which is essentially the one we use today, with 365 days in a year, and an added day every 4th year, or leap year.

RALPH: Of all of Caesar’s achievements, this is one that had a direct impact on people living in Shakespeare’s era.