A common year starting on Monday is any non-leap year (i.e., a year with 365 days) that begins on Monday, 1 January, and ends on Monday, 31 December. Its dominical letter hence is G. The most recent year of such kind was 2018 and the next one will be 2029 in the Gregorian calendar, or likewise, 2019 and 2030 in the Julian calendar, see below for more. This common year is one of the three possible common years in which a century year can begin on and occurs in century years that yield a remainder of 300 when divided by 400. The most recent such year was 1900 and the next one will be 2300.
Any common year that starts on Monday has two Friday the 13ths: those two in this common year occur in April and July.[globalize]From July of the year in this type of year to September in the year that follows this type of year is the longest period that occurs without a Friday the 13th, unless the following year is a leap year starting on Tuesday, in which case the gap is reduced to just 11 months, as the next Friday the 13th is already in June. From July of the year preceding this type of year to September in this type of year is the longest period that occurs without a Lucky Monday, in other words the 3rd day of the month being on a Monday (14 months). Leap years starting on Friday share this characteristic, from August of the common year preceding it to October of this type of year.
In the (currently used) Gregorian calendar, along with Sunday, Wednesday, Friday or Saturday, the fourteen types of year (seven common, seven leap) repeat in a 400-year cycle (20871 weeks). Forty-three common years per cycle or exactly 10.75% start on a Monday. The 28-year sub-cycle only spans across century years divisible by 400, e.g. 1600, 2000, and 2400.
In the Julian calendar, the fourteen types of year (seven common, seven leap) repeat in a 28-year cycle (1461 weeks). This sequence occurs exactly once within a cycle, and every common letter thrice.
As the Julian calendar repeats after 28 years that means it will also repeat after 700 years, i.e. 25 cycles. The year's position in the cycle is given by the formula ((year + 8) mod 28) + 1). Years 6, 12 and 23 of the cycle are common years beginning on Monday. 2017 is year 10 of the cycle. Approximately 10.71% of all years are common years beginning on Monday.