September 15, 1255: Day of the Week

September 15, 1255 was the 258^th day of the year 1255 in the Gregorian calendar. There were 107 days remaining until the end of the year. The day of the week was Wednesday.

The day of the week for September 15, 1255 under the old Julian calendar was Wednesday. Did you notice the similarity with the Gregorian calendar?

If you are trying to learn Spanish then this day of the week in Spanish is miércoles.

A person born on this day will be 769 years old today. If that same person saved a dollar every day starting at age 6, then by now that person has accumulated $278,718.00 today.

Here’s the September 1255 Gregorian calendar. You can also browse the full year monthly 1255 calendar.

Zodiac & Birthstone

Virgo is the zodiac sign of a person born on this day. Sapphire is the modern birthstone for this month. Agate is the mystical birthstone from Tibetan origin that dates back over a thousand years.

September 15, 1255 by the Numbers

• 280,910 days since September 15, 1255
• 769 years, 1 month, and 8 days ago
• 9,229 months since then
• September 15 is in the 37^th week of the year 1255 (ISO 8601)
• 40,130 weeks ago
• The year 1255 is not a leap year

Gregorian versus the old Julian calendar

A note to students, teachers, scholars and anyone else passionate about this topic. As stated in the front page, this website is using the Gregorian calendar as the basis for all “day of the week” computation whether or not the Gregorian calendar is relevant for the date in question (September 15, 1255). Educators should point out the primary reason why Pope Gregory XIII introduced a new calendar system in October 1582. That is, to make the computation for the annual date of Easter more accurate since it is the foundation of the Christian faith.

Even with that purpose in mind, the Gregorian calendar too will become out of sync. It has a known approximation error of about one day for every 7,700 years assuming a constant time interval between vernal equinoxes (which is not true). This is better compared to the one day for every 128 years error of the Julian calendar.

Now try another date like anniversaries, birthdays of someone you know or any other date that is special to you. Don’t forget to share the info to your friends, loved ones or social media followers. Who knows, they might appreciate and thank you for it.