The 800s decade ran from January 1, 800, to December 31, 809.
The 810s decade ran from January 1, 810, to December 31, 819.
The 820s decade ran from January 1, 820, to December 31, 829.
The 830s decade ran from January 1, 830, to December 31, 839.
The 840s decade ran from January 1, 840, to December 31, 849.
The 850s decade ran from January 1, 850, to December 31, 859.
The 860s decade ran from January 1, 860, to December 31, 869.
The 790s decade ran from January 1, 790, to December 31, 799.
The 780s decade ran from January 1, 780, to December 31, 789.
The 760s decade ran from January 1, 760, to December 31, 769.
The 700s decade ran from January 1, 700, to December 31, 709.
Year 840 (DCCCXL) was a leap year starting on Thursday in the Julian calendar, the 840th year of the Common Era (CE) and Anno Domini (AD) designations, the 840th year of the 1st millennium, the 40th year of the 9th century, and the 1st year of the 840s decade.
Year 810 (DCCCX) was a common year starting on Tuesday of the Julian calendar.
Year 809 (DCCCIX) was a common year starting on Monday of the Julian calendar, the 809th year of the Common Era (CE) and Anno Domini (AD) designations, the 809th year of the 1st millennium, the 9th year of the 9th century, and the 10th and last year of the 800s decade.
Year 805 (DCCCV) was a common year starting on Wednesday of the Julian calendar, the 805th year of the Common Era (CE) and Anno Domini (AD) designations, the 805th year of the 1st millennium, the 5th year of the 9th century, and the 6th year of the 800s decade.
Year 812 (DCCCXII) was a leap year starting on Thursday of the Julian calendar, the 812th year of the Common Era (CE) and Anno Domini (AD) designations, the 812th year of the 1st millennium, the 12th year of the 9th century, and the 3rd year of the 810s decade.
Year 785 (DCCLXXXV) was a common year starting on Saturday of the Julian calendar. The article denomination 785 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years. It is still used today in this manner.
Year 797 (DCCXCVII) was a common year starting on Sunday of the Julian calendar. The denomination 797 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
Year 826 (DCCCXXVI) was a common year starting on Monday of the Julian calendar, the 826th year of the Common Era (CE) and Anno Domini (AD) designations, the 826th year of the 1st millennium, the 26th year of the 9th century, and the 7th year of the 820s decade.
Year 829 (DCCCXXIX) was a common year starting on Friday of the Julian calendar.
