Calendar Wiki

This wiki's URL has been migrated to the primary fandom.com domain.Read more here

READ MORE

Calendar Wiki
Advertisement

Months have either 30 or 31 days. Patterns can be simple, i.e. 30:31 and 31:30, quarter-based, i.e. 31:30:30, 30:31:30 and 30:30:31, more complicated ,or totally irregular as in the Gregorian calendar.

On the one hand, six times 61 makes 366 days, thus either a 31st or a 30th day must be left out in leap years. On the other hand, four time 91 makes 364 days, thus either a 31st or a 32nd day must be added in common years, and another 31st, 32nd or 33rd in leap years, or a leap week has to be introduced which may make one month 37 or 38 days long in leap years.

End-of-year leap day[]

Month lengths in days, values for leap years shown in parentheses
Month J/G 31:30 30:31 31:30…30:31 30:31…31:30 31:30:30 30:31:30 30:30:31
January 31 ±0 −1 ±0 −1 ±0 −1 −1
February 28 (29) +2 (+1) +3 (+2) +2 (+1) +3 (+2) +2 (+1) +3 (+2) +2 (+1)
March 31 ±0 −1 ±0 −1 −1 −1 ±0
April 30 ±0 +1 ±0 +1 +1 ±0 ±0
May 31 ±0 −1 ±0 −1 −1 ±0 −1
June 30 ±0 +1 ±0 +1 ±0 ±0 +1
July 31 ±0 −1 −1 ±0 ±0 −1 −1
August 31 −1 ±0 ±0 −1 −1 ±0 −1
September 30 +1 ±0 ±0 +1 ±0 ±0 ±0
October 31 −1 ±0 ±0 −1 ±0 −1 −1
November 30 +1 ±0 ±0 +1 ±0 +1 ±0
December 31 −2 (−1) −1 (±0) −1 (±0) −2 (−1) ±0 (+1) ±0 (+1) +1 (+2)
Month starts in ordinal days, values for leap years shown in parentheses
Month J/G 31:30 30:31 31:30…30:31 30:31…31:30 31:30:30 30:31:30 30:30:31
January 001 ±0 ±0 ±0 ±0 ±0 ±0 ±0
February 032 ±0 −1 ±0 −1 ±0 −1 −1
March 060 (061) +2 (+1) +2 (+1) +2 (+1) +2 (+1) +2 (+1) +2 (+1) +1 (±0)
April 091 (092) +2 (+1) +1 (±0) +2 (+1) +1 (±0) +1 (±0) +1 (±0) +1 (±0)
May 121 (122) +2 (+1) +2 (+1) +2 (+1) +2 (+1) +2 (+1) +1 (±0) +1 (±0)
June 152 (153) +2 (+1) +1 (±0) +2 (+1) +1 (±0) +1 (±0) +1 (±0) ±0 (−1)
July 182 (183) +2 (+1) +2 (+1) +2 (+1) +2 (+1) +1 (±0) +1 (±0) +1 (±0)
August 213 (214) +3 (+2) +1 (±0) +1 (±0) +2 (+1) +1 (±0) ±0 (−1) ±0 (−1)
September 244 (245) +2 (+1) +1 (±0) +1 (±0) +1 (±0) ±0 (−1) ±0 (−1) −1 (−2)
October 274 (275) +1 (±0) +1 (±0) +1 (±0) +2 (+1) ±0 (−1) ±0 (−1) ±0 (−1)
November 305 (306) +1 (±0) +1 (±0) +1 (±0) +1 (±0) ±0 (−1) −1 (−2) −1 (−2)
December 335 (336) +1 (±0) +1 (±0) +1 (±0) +2 (+1) ±0 (−1) ±0 (−1) −1 (−2)
31:30...30:31 Month lengths with changes from Julian/Gregorian in days, values for leap years shown in parentheses
Month Length Start Length Position
January 31 001 ±0 ±0
February 30 032 +2 (+1) ±0
March 31 062 ±0 +2 (+1)
April 30 093 ±0 +2 (+1)
May 31 123 ±0 +2 (+1)
June 30 154 ±0 +2 (+1)
July 30 184 −1 +2 (+1)
August 31 214 ±0 +1 (±0)
September 30 245 ±0 +1 (±0)
October 31 275 ±0 +1 (±0)
November 30 306 ±0 +1 (±0)
December 30 (31) 336 −1 (±0) +1 (±0)
30:31...31:30 Month lengths with changes from Julian/Gregorian in days, values for leap years shown in parentheses
Month Length Start Length Position
January 30 001 −1 ±0
February 31 031 +3 (+2) −1
March 30 062 −1 +2 (+1)
April 31 092 +1 +1 (0)
May 30 123 −1 +2 (+1)
June 31 153 +1 +1 (±0)
July 31 184 ±0 +2 (+1)
August 30 215 −1 +2 (+1)
September 31 245 +1 +1 (±0)
October 30 276 −1 +2 (+1)
November 31 306 +1 +1 (±0)
December 29 (30) 337 −2 (−1) +2 (+1)
31:30 Month lengths with changes from Julian/Gregorian in days, values for leap years shown in parentheses
Month Length Start Length Position
January 31 001 ±0 ±0
February 30 032 +2 (+1) ±0
March 31 062 ±0 +2 (+1)
April 30 093 ±0 +2 (+1)
May 31 123 ±0 +2 (+1)
June 30 154 ±0 +2 (+1)
July 31 184 ±0 +2 (+1)
August 30 215 −1 +2 (+1)
September 31 245 +1 +1 (±0)
October 30 276 −1 +2 (+1)
November 31 306 +1 +1 (±0)
December 29 (30) 337 −2 (−1) +2 (+1)
30:31 Month lengths with changes from Julian/Gregorian in days, values for leap years shown in parentheses
Month Length Start Length Position
January 30 001 −1 ±0
February 31 031 +3 (+2) −1
March 30 062 −1 +2 (+1)
April 31 092 +1 +1 (0)
May 30 123 −1 +2 (+1)
June 31 153 +1 +1 (±0)
July 30 184 −1 +2 (+1)
August 31 214 ±0 +1 (±0)
September 30 245 ±0 +1 (±0)
October 31 275 ±0 +1 (±0)
November 30 306 ±0 +1 (±0)
December 30 (31) 336 −1 (±0) +1 (±0)
31:30:30 Month lengths with changes from Julian/Gregorian in days, values for leap years shown in parentheses
Month Length Start Length Position
January 31 001 ±0 ±0
February 30 032 +2 (+1) ±0
March 30 062 −1 +2 (+1)
April 31 092 +1 +1 (±0)
May 30 123 −1 +2 (+1)
June 30 153 ±0 +1 (±0)
July 31 183 ±0 +1 (±0)
August 30 214 −1 +1 (±0)
September 30 244 ±0 ±0 (−1)
October 31 274 ±0 ±0 (−1)
November 30 305 ±0 ±0 (−1)
December 31 (32) 335 ±0 (+1) ±0 (−1)
30:31:30 Month lengths with changes from Julian/Gregorian in days, values for leap years shown in parentheses
Month Length Start Length Position
January 30 001 −1 ±0
February 31 031 +3 (+2) −1
March 30 062 −1 +2 (+1)
April 30 092 ±0 +1 (±0)
May 31 122 ±0 +1 (±0)
June 30 153 ±0 +1 (±0)
July 30 183 −1 +1 (±0)
August 31 213 ±0 ±0 (−1)
September 30 244 ±0 ±0 (−1)
October 30 274 −1 ±0 (−1)
November 31 304 ±0 −1 (−2)
December 31 (32) 335 ±0 (+1) ±0 (−1)
30:30:31 Month lengths with changes from Julian/Gregorian in days, values for leap years shown in parentheses
Month Length Start Length Position
January 30 001 −1 ±0
February 30 031 +2 (+1) −1
March 31 061 ±0 +1 (±0)
April 30 092 ±0 +1 (±0)
May 30 122 −1 +1 (±0)
June 31 152 +1 ±0 (−1)
July 30 183 −1 +1 (±0)
August 30 213 −1 ±0 (−1)
September 31 243 ±0 −1 (−2)
October 30 274 −1 ±0 (−1)
November 30 304 ±0 −1 (−2)
December 32 (33) 334 +1 (+2) −1 (−2)

All items (12)

Advertisement