A **common year starting on Thursday** is any non-leap year (i.e. a year with 365 days) that begins on Thursday, 1 January, and ends on Thursday, 31 December. Its dominical letter hence is **D**. The most recent year of such kind was 2015 and the next one will be 2026 in the Gregorian calendar or, likewise, 2010 and 2021 in the obsolete Julian calendar, see below for more. This common year contains the most Friday the 13ths; specifically, the months of February, March, and November. Leap years starting on Sunday share this characteristic.

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## Gregorian Calendar

In the (currently used) Gregorian calendar, the 15 types of years repeat in a 400-year cycle (20871 weeks). Forty-four common years per cycle or exactly 11% start on a Thursday. The 28-year sub-cycle does only span across century years divisible by 400, e.g. 1600, 2000, and 2400.

## Julian Calendar

In the now-obsolete Julian calendar, the 15 types of years repeat in a 28-year cycle (1461 weeks). Each leap-year dominical letter occurs exactly once and every common letter thrice.

The final two digits of Julian years repeat after 700 years, i.e. 25 cycles. When starting to count in 2001 for instance, every 9th, 15th and 26th year of these Julian cycles is a common year that starts on a Thursday, i.e. ca. 10.71 % of all years. They are always 6 or 11 years apart.