Common year starting on Tuesday
A common year starting on Tuesday is any non-leap year (i.e. a year with 365 days) that begins on Tuesday, 1 January, and ends on Tuesday, 31 December. Its dominical letter hence is F. The current year, 2019, is a common year starting on Tuesday in the Gregorian calendar. The last such year was 2013 and the next such year will be 2030, or, likewise, 2014 and 2025 in the obsolete Julian calendar, see below for more. Any common year that starts on Sunday, Monday or Tuesday has two Friday the 13ths. This common year contains two Friday the 13ths in September and December. Leap years starting on Monday share this characteristic. From July of the year that precedes this year until September in this type of year is the longest period (14 months) that occurs without a Friday the 13th. Leap years starting on Saturday share this characteristic, from August of the common year that precedes it to October in that type of year.
February
February is also the only month of the calendar that, once every six years and twice every 11 years consecutively, either back into the past or forward into the future, has four full 7-day weeks. In countries that start their week on a Monday, it occurs as part of a common year starting on Friday, in which February 1st is a Monday and the 28th is a Sunday; this occurred in 1965, 1971, 1982, 1993, 1999 and 2010, and occur will again in 2021. In countries that start their week on a Sunday, it occurs in a common year starting on Thursday, with the next occurrence in 2026, and previous occurrences in 1987, 1998, 2009 and 2015. The pattern is broken by a skipped leap year, but no leap year has been skipped since 1900 and no others will be skipped until 2100.